autotronics - prof. ibrahim · pdf file10.3) electronic flasher circuit ... 11.5) electric...

Autotronics

By Prof.Shaikh Ibrahim Ismail

Department of Automobile Engineering M.H.S.S. College of Engineering

Mumbai

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Autotronics

www.ibrahimshaikh.com Prof. Shaikh Ibrahim Ismail

Table of Contents

CHAPTER NO. PAGE NO.

1 – BATTERIES .......................................................................................................................................................... 7

1.1) Battery Requirements ...................................................................................................................................................... 7

1.2) The Lead Acid Battery ....................................................................................................................................................... 7

1.3) Alkaline battery – Nicad Battery ..................................................................................................................................... 11

1.4) ZEBRA Battery ................................................................................................................................................................ 12

1.5) Sodium Sulfur Battery (NaS) ........................................................................................................................................... 12

1.6) Swing Battery ................................................................................................................................................................. 13

2 – FUEL CELLS ...................................................................................................................................................... 14

2.1) Introduction ................................................................................................................................................................... 14

2.2) Proton Exchange Membrane .......................................................................................................................................... 14

2.3) Alkaline fuel cells ............................................................................................................................................................ 15

2.4) High temperature fuel cells ............................................................................................................................................ 16

2.5) Reformers ....................................................................................................................................................................... 16

2.6) Other fuel cells ............................................................................................................................................................... 17

3 – 42 VOLT TECHNOLOGY ................................................................................................................................ 18

3.1) Introduction ................................................................................................................................................................... 18

3.2) Timeline of automotive electrical power source. ............................................................................................................ 18

3.3) Roadblocks ..................................................................................................................................................................... 18

3.4) Benefits .......................................................................................................................................................................... 20

3.5) Potential applications ..................................................................................................................................................... 20

3.6) Potential architectures ................................................................................................................................................... 22

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4 – CHARGING SYSTEM ....................................................................................................................................... 24

4.1) Introduction ................................................................................................................................................................... 24

4.2) Requirements of a Charging system ................................................................................................................................ 24

4.3) Charging system basics ................................................................................................................................................... 25

4.4) The Dynamo or Generator .............................................................................................................................................. 25

4.5) Regulators ...................................................................................................................................................................... 26

4.6) Alternators ..................................................................................................................................................................... 29

5 – STARTING SYSTEM ........................................................................................................................................ 32

5.1) Engine starting requirements ......................................................................................................................................... 32

5.2) Various Torque terms used with engine starting ............................................................................................................ 33

5.3) Starting motor ................................................................................................................................................................ 33

5.4) Starting motor drives ...................................................................................................................................................... 33

5.5) Starter motor solenoids .................................................................................................................................................. 38

5.6) Glow plug ....................................................................................................................................................................... 38

6 – IGNITION SYSTEMS ....................................................................................................................................... 40

6.1) Fundamentals ................................................................................................................................................................. 40

6.2) Capacitor discharge ignition ........................................................................................................................................... 41

6.3) Distributor less Ignition system ...................................................................................................................................... 42

6.3) Direct Ignition system ..................................................................................................................................................... 43

6.4) Hall effect pulse generator ............................................................................................................................................. 43

6.5) Inductive pulse generator ............................................................................................................................................... 44

6.6) Constant Dwell system ................................................................................................................................................... 44

6.7) Constant energy systems ................................................................................................................................................ 45

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6.7) Spark plug details ........................................................................................................................................................... 45

7 – WIRING .............................................................................................................................................................. 47

7.1) Electrical cables .............................................................................................................................................................. 47

7.2) Wiring harness system .................................................................................................................................................... 48

7.3) Multiplex wiring system ................................................................................................................................................. 49

7.4) Controller Area Network (CAN) ...................................................................................................................................... 50

8 – ELECTRONIC ENGINE CONTROLS ............................................................................................................. 52

8.1) Electronic Control Module (ECM) .................................................................................................................................... 52

8.2) Electronic spark timing ................................................................................................................................................... 54

8.3) Electronic spark control .................................................................................................................................................. 54

8.4) Idle speed control system ............................................................................................................................................... 54

8.5) Air management system ................................................................................................................................................. 55

9 – SENSORS AND ACTUATORS ........................................................................................................................ 56

9.1) SENSORS PRINCIPLES ...................................................................................................................................................... 56

9.2) Automotive sensors explanation .................................................................................................................................... 58

9.3) Actuators ........................................................................................................................................................................ 62

9.4) Some Automotive Actuators........................................................................................................................................... 64

10 – LIGHTING ....................................................................................................................................................... 65

10.1) Types of lamps .............................................................................................................................................................. 65

10.2) Head lamps ................................................................................................................................................................... 66

10.3) Electronic flasher circuit ............................................................................................................................................... 69

11 – ACCESSORIES ................................................................................................................................................ 71

11.1) Function of Instrument panel ....................................................................................................................................... 71

11.2) Visual displays .............................................................................................................................................................. 72

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11.5) Electric horn ................................................................................................................................................................. 73

11.6) Wipers .......................................................................................................................................................................... 74

11.7) Fuel pump .................................................................................................................................................................... 74

11.8) Power operated windows ............................................................................................................................................. 75

12 – TELEMATICS ................................................................................................................................................. 77

12.1) Introduction.................................................................................................................................................................. 77

12.2) Telematics architecture ................................................................................................................................................ 77

12.3) Services and applications .............................................................................................................................................. 78

13 – INTELLIGENT VEHICLE SYSTEMS .......................................................................................................... 80

13.1) Antilock Braking System ............................................................................................................................................... 80

13.2) Active suspension ......................................................................................................................................................... 83

13.3) Traction control ............................................................................................................................................................ 84

13.4) Electric power steering ................................................................................................................................................. 85

13.5) Global Positioning System ............................................................................................................................................ 85

13.6) Adaptive Cruise Control ................................................................................................................................................ 86

13.8) Drive by wire ................................................................................................................................................................ 86

APPENDIX – I – LIST OF FIGURES, GRAPHS, TABLES ................................................................................ 88

APPENDIX – II –SIMPLIFIED WIRING CIRCUIT OF A CAR ........................................................................ 90

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1 – Batteries

Requirements, construction, principle of operation and working of the following types of batteries: Lead acid, Al-

kaline, ZEBRA, Sodium Sulphur and Swing battery. Ratings, charging, Maintenance, and testing of Lead-Acid battery

1.1) Battery Requirements

The vehicle battery is used as a source of energy when the engine, and thus the alternator is not running. The bat-

tery has a number of requirements they are as follows:

To provide power storage and be able to supply it quickly enough to operate the vehicle starter motor.

To allow the use of parking lights for automobile for a reasonable amount of time.

To allow operation of accessories when the engine is not running.

To act as a swamp to damp out fluctuations of system voltage.

To allow dynamic memory and alarm systems to remain active when the vehicle is left for some time.

The battery should carry out all the above in a temperature range, usually from -30oC to +70oC.

1.2) The Lead Acid Battery

1.2.1) Construction

The basic construction of a nominal 12 V lead acid battery consists of six cells connected in series. Each cell, pro-

ducing 2V, is housed in an individual compartment with a polypropylene, or similar case. The active material is held in

grids or baskets to form positive and negative plates. Separators made from micro porous plastic insulate these plates

from each other. The grids connecting the strips and the battery posts are made of lead alloy. For many years this was

lead antimony (PbSb) but lately it has been lead calcium (PbCa). The newer materials cause less gassing of the electro-

lyte when fully charged. This is one of the main reasons why sealed batteries became usable as the water loss was con-

siderably reduced. However, even modern batteries have a small amount of vent to release the little pressure that

builds due to the little gassing.

1.2.2) Battery Ratings

An automobile battery is rated in one of the following ways

Ampere hour capacity (A-h): This describes how much current a battery is able to deliver for 10 or 20 hrs. It is seldom used now days. It is denoted by the amount of current it can supplied multiplied by the amount of time it can supply that current. For example, a battery with a capacity of 44 A-h indicates that the battery is able to supply 2.2Amps for 20hrs before it is completely discharged to a voltage of 1.75 Amps.

Reserve capacity: This is the system that is now used on most batteries. It is quoted as a time the battery will supply 25A at 25oC to a final voltage of 1.75V per cell. This is used to give an indication of how long will a battery could run the car if the engine charging system was not working. Typically a battery with 44 A-h capacity has a reserve capacity of 60 mins.

Cold Cranking Amperes (CCA): This is a rating defining the battery performance at high current output at low tempera-tures. A typical value of 170A means that the battery will supply this current for one minute at a temperature of -18oC, at which point the cell voltage will fall to below 1.4V. It should be noted that the overall output of the battery is more when spread over a big time, this is because the chemical reaction can be carried out only at a certain speed.

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Chapter 2 – Fuel Cells


Graph – 1.2.2.1 Battery rating relations

1.2.3) Working

A fully charged lead acid battery consists of Lead peroxide (PbO2) as positive plates and spongy lead (Pb) as nega-

tive plates, immersed in a diluted solution of sulfuric acid (H2O + H2SO4). The diluted electrolyte has a relative density of

1.28.

When sulfuric acid is in aqueous solution, it dissociates into 2H++ and SO4- - ions. The voltage of a cell is created

when the electrons of the electrodes ions are forced into the solution by solution pressure. Lead will give up 2 positively

charged atoms into the solution, thus freeing 2 electrons. Thus electrode now has excess of electrons and will become

negative w.r.t the electrolyte. If another electrode is immersed in the electrolyte, a potential difference is created and

the cell will conduct. This is the principle of the lead acid battery.

DURING DISCHARGING:

At positive plate: Lead peroxide tends to combine with dissociated H++ and become lead oxide and water. At the

same time this lead formed (Pb++) tends to combine with sulphate and form lead sulphate. The reaction is as given be-

low

PbO2+4H++2e- PbSO4+2H2O

At negative plate: The lead looses 2 electrons and becomes positively charged, this then combines with the sulfate

in the electrolyte and gives lead sulfate as follows

Pb+SO4- -PbSO4+2e-

DURING CHARGING:

The process is reverse of that of above.

At positive plate:

PbSO4 – 2e- +2H2O PbO2+H2SO4+2H++

At negative plate:

PbSO4+2e-+2H+Pb+H2SO4

NET REACTION

PbO2+2H2SO4+Pb2PbSO4+2H2O

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1.2.4) Battery voltages.

Acid

density

Cell

Voltage

Battery

voltage

%

Charge

1.28 2.12 12.7 100

1.24 2.08 12.5 70

1.20 2.04 12.3 50

1.15 1.99 12.0 20

1.12 1.96 11.8 0

Table – 1.2.4.1 Battery voltages at different charges

1.2.4) Charging

Usually, every battery manufacturer has got his own charging specifications. However, in a general aspect, the fol-

lowing is considered as considerable. The charging requires to ‘put back’ the same ampere hour capacity in the battery,

as was initially. Thus the question is not how much to charge but at what rate to charge. There are a number of ways to

charge a battery, they are as follows:

The old convention was to charge battery at one tenth of Ah capacity for about 10 hrs or less. However this is now ob-solete

To charge at 1/16th of reserve capacity, again for 10 hrs or less

To charge at 1/40th of cold start performance figure, again for up to 10 hrs.

Clearly, if a battery is only half discharged, only half the time is required to charge it.

All the above methods opt for a constant current charging source. However, a constant voltage charging system is best for battery charging. This means that the charging source voltage (that includes the car charging system) is held at a constant level, and the current flowing to charge depends upon the amount of charge in the battery.

Another way to charge the battery is boost charge it. It is popular method and is applied in many workshops. In this method, the battery is charged at about 5 times the normal recommended charging rate and the battery will attain 70-80% of its full charge in about one hour. However, during this method, the battery temperature must not exceed 43oC

1.2.5) Maintenance

The modern Lead acid battery is maintenance free. However, older and conventional batteries require electrolyte

topping up. Battery posts are still prone to corrosion and the usual hot water washing is required sometimes. To pre-

vent corrosion, petroleum jelly is applied to the terminals as a precautionary measure also. If the battery case and the

top remains clean, self discharging can be avoided.

It is not advisable to let the state of charge of the battery fall below 70% or less for long periods as the sulfate on

the plates can harden, making recharging difficult.

Sulfation of batteries is another problem. Sulfation refers to the process whereby a lead-acid battery (such as a car

battery) loses its ability to hold a charge after it is kept in a discharged state too long due to the crystallization of lead

sulfate.

Over time, lead sulfate converts to the more stable crystalline form, coating the battery's plates. Crystalline lead

sulfate does not conduct electricity and cannot be converted back into lead and lead oxide under normal charging con-

ditions. As batteries are "cycled" through numerous discharge and charge sequences, lead sulfate that forms during

normal discharge is slowly converted to a very stable crystalline form. This process is known as sulfation. in such a case

the battery requires replacement.

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1.2.6) Testing

There are various ways to test a lead acid battery, they are as follows.

Hydrometer: it comprises of a syringe that draws electrolyte from the cell, and a float that will float at a particular

depth in the electrolyte according to the relative density of the electrolyte. The density or specific gravity is then read

from a graduated scale. A fully charged cell should show 1.28. However as most batteries today are maintenance free

and thus sealed, a hydrometer can no longer be used, thus batteries are tested for their voltage and the charge deter-

mined, refer to table 1.2.4.1.

Fig – 1.2.6.1 A Hydrometer

Heavy Duty Discharge Tester: it is as shown in Fig 1.2.6.2. it consists of a low value resistor and a voltmeter con-

nected with a pair of heavy duty test prods. The test prods are firmly pressed against the battery terminals and the

voltmeter reads the voltage at a current discharge of about 200-300A. A fully charged battery should read about 10 V

for 10 seconds. A sharply falling voltage of below 3V indicates unserviceable conditions. A zero reading indicates an

open circuit cell. When using this instrument, the following must be noted.

Blow gently over the battery to remove flammable gasses.

The test rods must be positively and firmly pressed against the battery terminals to prevent sparking.

It should not be used when the battery is on charge.

Fig – 1.2.6.2 Heavy Duty discharge tester.

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1.3) Alkaline battery – Nicad Battery

Lead acid batteries are good and most suitable, however they cannot withstand electric abuse such as repeated

charging, discharging and sometimes heavy discharge and overcharge. Alkaline batteries are better counterparts

Advantages of alkaline batteries are

Alkaline batteries are much better in withstanding electric abuse.

It is immune to heavy discharge.

It also does not get spoilt on over charging as during charging Cadmium oxide changes to cadmium and hence no fur-ther reaction can take place.

Disadvantages of alkaline batteries are

They are more bulky.

Have low energy efficiency

Are more costly

Considering ‘lifetime’ performance, it is useful for some applications. Bus and coach companies are employing such

batteries. The most used battery in vehicles is the Nickel – cadmium (Nicad) battery.

Construction:

Positive plate: Nickel hydrate (NiOOH)

Negative plate: Cadmium

Electrolyte: Potassium hydroxide and water (KOH + H2O)

Reaction:

2NiOOH+Cd+H2O+KOH2Ni(OH)2+CdO2+KOH

The above is a simplified reaction. The electrolyte does not change during reaction and hence relative density can-

not be an indication of charge.

Voltage:

The cell voltage is 1.4V but falls rapidly to 1.3V as soon as discharge begins. At 1.1V, cell is fully discharged.

Fig – 1.3.1 Simplified Nicad battery.

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1.4) ZEBRA Battery

Zebra stands for Zero Emissions Battery Research Activity. The zebra battery, which operates at 250°C, utilizes mol-

ten chloro-aluminate (NaAlCl4), which has a melting point of approximately 160 °C, as the electrolyte. The negative elec-

trode is molten sodium. The positive electrode is nickel in the discharged state and nickel chloride in the charged state.

Because nickel and nickel chloride are nearly insoluble in neutral and basic melts, intimate contact is allowed, providing

little resistance to charge transfer. Since both NaAlCl4 and Na are liquid at the operating temperature, a sodium-

conducting β-alumina ceramic is used to separate the liquid sodium from the molten NaAlCl4.

The ZEBRA battery has an attractive specific energy and power (90 Wh/kg and 150 W/kg). The liquid electrolyte

freezes at 157 °C, and the normal operating temperature range is 270–350 °C

1.5) Sodium Sulfur Battery (NaS)

NaS consists of a cathode of liquid sodium into which is placed a current collector. This is a solid electrode of beta

alumina. A metal can that is in contact with the anode (a sulfur electrode) surrounds the whole assembly.

The running temperature of the cell is 300-350oC. A heater rated at a few hundered watts is required as part of the

charging circuit which needs to be on even when the car is not running.

Each cell is small, using about 15g of sodium each. This means that the cells can be distributed around the vehicle,

making packaging easy. The problem today is to find a suitable, cheap casing of the cell, due to corrosive nature of so-

dium. Highly costly chromized coating is used today.

The cell voltage is about 2.1V.

Fig – 1.5.1 Sodium Sulfur battery

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1.6) Swing Battery

All the alternate batteries discussed above consist of high temperature operation of batteries. It is of importance

to develop a battery that operates in a normal temperature range. Swing batteries are such batteries.

Swing batteries use lithium ions. These batteries have a cathode made of transition metal oxides. Lithium ions are

in constant movement between these very thin electrodes in a non aqueous electrolyte. The swing process takes place

at a normal temperature and gives a very high average cell voltage of approximately 3.5V, which is highest.

Fig – 1.6.1 Swing Battery

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2 – Fuel cells

Introduction to fuel cells and fuels used. Construction operation of Proton Exchange Memrane, Alkaline Electro-

lyte, Medium and High temperature fuel cells, Reformers.

2.1) Introduction

A fuel cell is an electrochemical energy conversion device. It produces electricity from various external quantities

of fuel (on the anode side) and an oxidant (on the cathode side). These react in the presence of an electrolyte. General-

ly, the reactants flow in and reaction products flow out while the electrolyte remains in the cell. Fuel cells can operate

virtually continuously as long as the necessary flows are maintained.

Fuel cells are different from batteries in that they consume reactant, which must be replenished, whereas batter-

ies store electrical energy chemically in a closed system. Additionally, while the electrodes within a battery react and

change as a battery is charged or discharged, a fuel cell's electrodes are catalytic and relatively stable.

2.2) Proton Exchange Membrane

Proton exchange membrane fuel cells, also known as polymer electrolyte membrane fuel cells (PEMFC), are a type

of fuel cell being developed for transport applications as well as for stationary and portable applications. Their distin-

guishing features include lower temperature/pressure ranges (50-100 degrees C) and a special polymer electrolyte

membrane.

2.2.1) Construction and Working

A proton exchange membrane fuel cell transforms the chemical energy liberated during the electrochemical reac-

tion of hydrogen and oxygen to electrical energy, as opposed to the direct combustion of hydrogen and oxygen gases to

produce thermal energy.

A stream of hydrogen is delivered to the anode side of the membrane-electrode assembly (MEA). At the anode

side it is catalytically split into protons and electrons. This oxidation half-cell reaction is represented by:

H22H++2e-

The newly formed protons permeate through the polymer electrolyte membrane to the cathode side. The elec-

trons travel along an external load circuit to the cathode side of the MEA, thus creating the current output of the fuel

cell.

Meanwhile, a stream of oxygen is delivered to the cathode side of the MEA. At the cathode side oxygen molecules

react with the protons permeating through the polymer electrolyte membrane and the electrons arriving through the

external circuit to form water molecules. This reduction half-cell reaction is represented by:

4H++4e-+O22H2O

To function, the membrane must conduct hydrogen ions (protons) but not electrons as this would in effect "short

circuit" the fuel cell. The membrane must also not allow either gas to pass to the other side of the cell, a problem

known as gas crossover. Finally, the membrane must be resistant to the reducing environment at the cathode as well as

the harsh oxidative environment at the anode.

Splitting of the hydrogen molecule is relatively easy by using a platinum catalyst. Unfortunately however, splitting

the oxygen molecule is more difficult, and this causes significant electric losses

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AutotronicsAutotronics-15

Chapter 3 – 42 Volt Technology


Fig – 2.2.1.1 PEM Fuel cell

2.3) Alkaline fuel cells

The alkaline fuel cell (AFC), also known as the Bacon fuel cell after its British inventor, is one of the most developed

fuel cell technologies and is the cell that flew Man to the Moon. The Apollo series and the shuttle both used AFCs.

2.3.1) Working

The fuel cell produces power through a redox reaction between hydrogen and oxygen. At the anode, hydrogen is

oxidized according to the reaction:

H2+2OH-H2O+2e-

Producing water and releasing two electrons. The electrons flow through an external circuit and return to the

cathode, reducing oxygen in the reaction:

O2+2H2O+4e-4OH-

Producing hydroxide ions. The net reaction consumes one oxygen molecule and two hydrogen molecules in the

production of two water molecules. Electricity and heat are formed as by-products of this reaction.

The two electrodes are separated by a porous matrix saturated with an aqueous alkaline solution, such as potassi-

um hydroxide (KOH). Aqueous alkaline solutions do not reject carbon dioxide (CO2) so the fuel cell can become "poi-

soned" through the conversion of KOH to potassium carbonate (K2CO3). Because of this, alkaline fuel cells typically op-

erate on pure oxygen, or at least purified air and would incorporate a 'scruber' into the design to clean out as much of

the carbon dioxide as is possible.

2.3.2) Construction

Because of this poisoning effect, two main variants of AFCs exist: static electrolyte and flowing electrolyte.

Static, or immobilized, electrolyte cells of the type used in the Apollo space craft and the Space Shuttle typically

use an asbestos separator saturated in potassium hydroxide. Water production is managed by evaporation out the an-

ode, as pictured in Fig 2.3.2.1, which produces pure water that may be reclaimed for other uses. These fuel cells typical-

ly use platinum catalysts to achieve maximum volumetric and specific efficiencies.

Flowing electrolyte designs use a more open matrix that allows the electrolyte to flow either between the elec-

trodes (parallel to the electrodes) or through the electrodes in a transverse direction.

In the case of "parallel flow" designs, greater space is required between electrodes to enable this flow, and this

translates into an increase in cell resistance, decreasing power output compared to immobilized electrolyte designs.

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Chapter 2 – Fuel cells


Fig – 2.3.2.1 Alkaline fuel cell

2.4) High temperature fuel cells

Low temperature fuel cells are operated at a membrane temperature of approx. 80 degrees Celsius. If the tem-

perature greatly exceeds this value fuel cell performance breaks down and irreparable damage is done to the fuel cell .

This is why LT fuel cell vehicle prototypes – should they be able to pass driving test cycles similar to a combustion en-

gine – place very high requirements on the cooling system, making it very expensive. In addition, in an LT system the

supply of hydrogen gas and air must be continuously humidified, because otherwise the production of energy will break

down, permanently damaging the fuel cell and bringing the electric engine being powered to a stop. This humidification

also takes space, weight and money.

The high temperature membrane developed by Volkswagen can in combination with newly designed electrodes

be “driven” at temperatures of up to 160 degrees at the same output of power. A medium operating temperature of

120° C is intended for vehicle operation. And this without additional humidification. A distinctly simpler cooling system

and water management is sufficient here, significantly reducing the need for space, weight and money!

2.5) Reformers

The basic necessity of any fuel cells is to obtain supply of hydrogen. Reformers are systems that can convert hydro-

carbons, alcohols etc into pure hydrogen. One very significant reformer is the steam reformer.

It is also the least expensive method. At high temperatures (700 – 1100 °C) and in the presence of a metal-based

catalyst (nickel), steam reacts with methane to yield carbon monoxide and hydrogen.

CH4 + H2O → CO + 3 H2

Additional hydrogen can be recovered by a lower-temperature gas-shift reaction with the carbon monoxide pro-

duced. The reaction is summarised by:

CO + H2O → CO2 + H2

Steam reforming of liquid hydrocarbons is seen as a potential way to provide fuel for fuel cells. The basic idea is

that for example a methanol tank and a steam reforming unit would replace the bulky pressurized hydrogen tanks that

would otherwise be necessary. This might mitigate the distribution problems associated with hydrogen vehicles. How-

ever, there are several challenges associated with this technology:

The reforming reaction takes place at high temperatures, making it slow to start up and requiring costly high tempera-ture materials.

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Sulfur compounds present in the fuel poison certain catalysts, making it difficult to run this type of system from ordi-nary gasoline. Some new technologies have overcome this challenge, however, with sulfur-tolerant catalysts.

The carbon monoxide (CO) produced by the reactor poisons the fuel cell, making it necessary to include complex CO-removal systems.

2.6) Other fuel cells

Apart from the cells mentioned above, there are several other types of fuel cells used. Some of them are as listed

below

Phosphoric Acid Fuel Cell (PAFC): it has a potential use in small stationary power generation systems. It operates at a higher temperature than the PEMs and hence requires longer warm-up time. This makes them unsuitable for automo-bile applications.

Solid Oxide Fuel Cell (SOFC): they are best suited for large scale stationary power generators to provide electricity for factories or towns. It operates at temperatures of 1000oC and hence it has reliability as one major problem. However, it generates a major by product i.e. steam. This steam can be used to run turbines which can also generate more electrici-ty, this increases overall efficiency of the system.

Molten Carbonate Fuel Cell (MCFC): these fuel cells also generate steam which can be used similarly as that in SOFC. They operate though at about 600oC which makes them more cheaper than the SOFC.

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3 – 42 Volt technology

Introduction, Transition from 12V to 42V electrical system, Need for 42V automotive electrical system, 42V au-

tomotive power system, Method of controlling 12V system in 42V architecture. Present developments in 42V technol-

ogy.

3.1) Introduction

As vehicles have become more and more complex with n number of accessories such as multimedia, climate con-

trol, safety systems, and then are the engine and transmission systems such as sensors and actuators, fuel pumps, cool-

ant pumps etc. All these are increasing the load on the electric battery of a car. If the car is being kept on loaded with

such amenities, soon then 12 V system of a car will no longer be able to cope with the power demands. Even today,

some high end car manufacturers are being faced with this problem of electric energy. Moreover, with more electric

power on board, some systems that use hydraulic or mechanical principles can be converted to electric thereby reduc-

ing overall long term cost.

Today’s 12V batteries are charged by 14V supply. A 42V technology offers a 4 fold leap in the power output, and

thus the charging power as well. Hence it is termed as 42V (i.e. 14V x 4 = 42V) technology.

3.2) Timeline of automotive electrical power source.

The various milestones in the automotive electrical power source is as given below:

Invention of cars used 6 V technology

1912: Electric starter motor developed which changed electric needs of a car.

Early 1950s: Implementation of high powered headlights. Introduction of high compression V8 engines with higher spark demands.

Late 1950s: 6 volt batteries transited to 12V batteries. It is sometimes referred to as 14V also as the charging voltage for the battery was 14V. transition was easy as the new systems utilized 6V technology that was simply adapted to work on higher voltages.

1960s and 70s: Transistors and integrated circuits replaced vacuum tubes. Radios became compact and portable and thus were fitted in cars. Along with this came the requirement of instantaneous warm-up, electronic engine controls, seat belt/starter interlock systems were the first to show up on cars.

1980s: Power demands of cars growing by 4% a year, and we are already crossing the 2kW mark. 3kW is a kind of break-ing point for the 12V battery system. At 3kW power consumption, 79% of engine power will not make it to the driveline!

1990s: Thought of ‘beltless’ engines, which means engine drives only drivelines. Compressor fuel pumps etc driven by alternate electric source. It was here that 42V technology was coined.

1996: Mercedes sponsored MIT students completed report on 42V technology after a detailed study of American and German OEMs.

2002-2003: Early predictions of 1990s showed that 42V systems would be introduced in cars by this year. However many roadblocks prevented it from hitting the road.

2004: European OEMs claim to have ready technology to incorporate the 42V systems.

2010: Estimated time by which 42V technology will be introduced in production cars.

3.3) Roadblocks

Inspite of the potential advantages of the technology, the industry is not completely sure on the profit aspects of

the system. A few roadblocks in transition is as given below

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Economic hurdles:

1. Is market ready yet: Although people are increasing in their automotive power demand, will they pay for such a change in technology? It is a fact that most power hungry vehicles are only the high end luxury cars. What about the low end versions?

2. Today’s electric components may become obsolete: Components used today work on 12V technology. Shifting to a 42V technology means that all these components need to be changed and upgraded, or additional circuitry be intro-duced to incorporate the same old components.

3. Are OEMs ready: With 90% of the electric components purchased from OEMs, it is necessary that all these OEMs need to modify their production lines in order to manufacture the new technologically adaptable components. This increases the overall cost on the consumer.

4. Change in standards: International and local government automotive standards are based on 12V technology. To incor-porate the new technology, theses institutes need to create workgroups and redefine the standards, which again is a costly process.

5. Tools and equipment: Today’s after sales service workshops such as garages etc have to incorporate new tools to test and diagnose the car on the new technology. This means replacement of costly engine analyzers and many such equip-ment.

6. Wait till the need arises: Due to many of these disadvantages, many automotive and supplier companies are simply looking to the other way. This means that they wish to tackle the problem only when an urgent need has arised.

Technical hurdles:

1. Roadside assistance: Jumpstarting a 42V technology-run vehicle by an older version can result in catastrophic results, causing permanent damage to the 12V system. This also needs to be incorporated in the research procedure.

2. Lighting: Today’s vehicles, mostly use tungsten filament bulbs. A 42V technology means that the filaments need to be further thinned out in order to produce the same luminosity. This possesses a serious challenge to OEMs. An alternate is to use white lights known as High Intensity Discharge (HID), but then they are costly.

3. Voltage regulations: To incorporate today’s technology of 12 V in further 42V technology requires some sort of DC to DC conversion. However DC to DC converters are not cheap, and hence would add on to increase in cost. One way to solve this problem is using pulse width modulation (PWM) which supplies the electric energy in pulses. Thus the electric energy received will be eventually less.

4. Packaging: Environment under the hood of a car and in fact anywhere in the car is very abusive. Temperatures, humidi-ty, pressure etc reach extremities which needs proper care in incorporating the new technology.

5. Corrosion: There is a divide in the technical community regarding this. Some of the people feel that the increased volt-age will corrode exposed wires faster, while others think that it would not be a problem.

6. Arcing: An increased electrical energy will give rise to Arcing. This, if occurred in the vicinity of the fuel supply line, could result in catastrophic results. The arcing however would eventually depend upon the capacitance of the system, yet this needs to be considered.

Myth about Safety

It is said by many scientists that the 42V technology would increase safety risks. However, tests conducted as early as 1930s and lately by the German standard committee concluded that voltages below 60V are not harmful. And as the voltages of the 42V technology is below that level, there is no safety problem as such.

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3.4) Benefits

Current Technology 42 V technology

Electric power steering More power with improved fuel economy

Electric brakes Redundant power supplies

Power windows, power

seat belts,

Power hatchback lifts

Reduced size and mass of motors, hence

more efficient

Heated catalytic converter Greater efficiency, smaller units hence

packaging improved

Mobile multimedia More power available for DVD players, fax,

GPS, mp3 etc

Electric water pumps Improved efficiency with longer service life

Selected Engine manage-

ment systems (eg, EGR

valves, Throttle valves etc

etc)

Reduced size and mass hence increased per-

formance

Fuel pumps Reduced size, hence packaging

Heated seats Faster heating, hence increased luxury level

Table – 3.4.1 Benefits of 42V technology

Along with the above benefits, a few systems are elaborated below:

Efficiency: The alternator operation requires a lot of fuel. With the present day 14V alternators, the engine efficiency over the entire speed range is not more than 60%. In a mixed driving environment (city and highways) more than 0.5 gallons of fuel is required for 1Kw load output per 65 miles. The 42V technology will bring it down to about 0.15 gallons.

Wiring Harness: The wire size will reduce as the increased voltage means less current can be supplied to almost all ap-plications. Thus the wiring harness flexibility will increase.

Increased performance: There are 3 ways in which the performance will increase. One is the decrease in amount of power drained out of the power train. Thus a potential increase in fuel economy. And lastly is the possibility of including additional equipments in the car, preferably for driver’s assistance.

Cheaper semiconductors: This is achieved in semiconductors. Today’s semiconductors are built in with protection against high voltages (of up to 60V!!). However a carefully designed, new 42V system will remove this need and smaller semiconductors can be used which will enhance multiplexing.

Reduced Mass/cost ratio: Weights of solenoids decrease almost linearly with the increase in voltage. For motors the decrement in weight is slightly less dramatic as the gears etc will still be there. However, Reiner Emig, VP-Engineering at Bosch says that a weight reduction of up to 20% can be achieved.

3.5) Potential applications

Integrated Starter Generator (ISG)

The ISG is a novel idea which combines the starter and generator and works on 42V technology. The ISG is usually

mounted directly on the crankshaft between the engine and the transmission, owing to its compact size. It electromag-

netically transmits the force to the crankshaft when the key is turned, and starts the engine at a fraction of time

(around 0.2s) which would be usually required in a conventional system. The reason for this that it does not have to

drive the pinion in mesh with the ring gear and this saves time. The ISG also eliminates most engine starting noise by

electromagnetically damping it.

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It is also termed as ‘stop-start’ system due to its reduced starting time. For this it can be used to reduce fuel econ-

omy and emissions. They have thus a potential for acceleration boost and breaking energy regeneration. Thus the car

can have no start switch, and the car would simply accelerate on application of the accelerator pedal. And the engine

would switch off on application of brake, hence start-stop.

Moreover, the ISG can create 10kW of power which is a requirement of 42V technology.

Electromagnetic valves

Most piston engines today employ a camshaft to operate poppet valves. This consists of a cylindrical rod running

the length of the cylinder bank with a number of oblong lobes or cams protruding from it, one for each valve. The cams

force the valves open by pressing on the valve, or on some intermediate mechanism, as they rotate.

Another problem with the system is the added weight and the option of having only one or to a max of 3 or 4 valve

timings based on different valve lobes for each valve.

One of the approaches designed to overcome these problems, but which has proved difficult to implement, is

Camless valve trains using solenoids or magnetic systems. Camless engines would not only be more efficient in terms of

mechanical energy, they would also be more flexible, as the valves could be computer-controlled. Infinitely variable

valve timing would be possible, though variable valve lift would be more difficult. Valeo estimates that the efficiency of

a camless engine would be 20% greater than a comparable camshaft-operated engine.

Another ability is to use cylinder deactivation. This means that 2 cylinders of a V8 engine can be deactivated by

temporarily closing the inlet valve and at the same time opening the exhaust valve of those cylinders. Thus the V8 en-

gine will function as a V6 engine with an extra pair of redundant pistons. This can be done at low loads. Cadillac has in-

troduced such engines in their prototypes.

Also, all the valves can be opened just before starting the engine, relieving the compression pressure and decreas-

ing cranking torque requirement. Even more intriguing is the ability to combine it with direct fuel injection and start an

engine statically using no external rotator means. Valves of the appropriate cylinders would be closed and an amount of

fuel will be injected, which will then be sparked, thus engine is started!

Electrically heated catalytic converter

Exhaust gas emissions are of great importance today. Most of these exhaust gasses are controlled by the use of a

catalytic converter. However a problem with the catalytic converter is that it only operates at a higher temperature.

This incorporates the need of providing means of heating the converter when it is not hot, during starting and in cold

atmosphere. With 42V technology, additional power can be supplied to heat the catalytic converter.

Electrical active suspension

Active suspension refers to the system that keeps the passenger compartment in the same horizontal line, or flat

trajectory when the car encounters a pot hole or a bump. Active suspension is an automotive technology that controls

the vertical movement of the wheels via an onboard system rather than the movement being determined entirely by

the surface on which the car is driving. The system therefore virtually eliminates body roll and pitch variation in many

driving situations including cornering, accelerating, and braking.

Electromagnetic recuperative active suspension is one such type that has high power requirement, which can be

easily answered by 42V technology. This type of active suspension uses linear electromagnetic motors attached to each

wheel independently allowing for extremely fast response and allowing for regeneration of power used through utiliz-

ing the motors as generators.

This technology allows car manufacturers to achieve a higher degree of both ride quality and car handling by keep-

ing the tires perpendicular to the road in corners, allowing for much higher levels of grip and control.

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Electronic power steering

Electric power steering (EPS or EPAS) is designed to use an electric motor to reduce effort by providing assist to the

driver of a vehicle. Most EPS systems have variable assist, which allows for more assistance as the speed of a vehicle

decreases and less assistance from the system during high-speed situations. This functionality requires a delicate bal-

ance of power and control that has only been available to manufacturers in recent years. The EPS system has replaced

the hydraulic steering system (HPS or HPAS) in many passenger cars recently. Although EPS is so far limited to passen-

ger cars, as a higher voltage electrical system is necessary to operate EPS in larger vehicles.

Electromechanical brakes (EMB)

Brake-by-wire represents the replacement of traditional components such as the pumps, hoses, fluids, belts and

brake boosters and master cylinders with electronic sensors and actuators. Once the driver inputs a brake command to

the system via the brake pedal, four independent brake commands are generated by the ECU based on high level brake

functions such as anti-lock braking system (ABS) or vehicle stability control (VSC). These command signals are sent to

the four electric calipers (e-calipers) via a communication network. Thus in an EMB, ABS, traction control, vehicle stabil-

ity and panic brake assist will not be controlled by hydraulic but electrically operated gearboxes, monitored by the ECM.

Electric water and oil pumps

In most vehicles today, the water pump required for cooling and the oil pump for engine lubrication is driven by a

V-belt which connects these pump pulleys to the crank pulley. This offers direct loss of engine power. With the more

electric energy available with 42V technology, these components can be driven by motors, thereby removing load from

the engine and resulting in better fuel economy.

Electric Air Conditioning

In today's cars, the air conditioner compressor is driven by the engine. This creates a similar problem as discussed

above. An electric motor is the best solution for this problem. Also, the need for an AC arises not only when the engine

is driving but also when the engine is off, like in traffic jams. 42V technology solves this problem.

Batteries

On a start-stop system, where in the engine will stop each time the vehicle stops, say at a traffic light. It is esti-

mated that the car would need to crank the engine about 50,000 times a year compared to about 1000 times a year. As

a conventional lead acid battery has a limited charging-discharging cycle, it cannot be used in that case. In urban condi-

tions such as cities, with a large number of traffic jams and traffic lights, the battery needs to supply sharp bursts of en-

ergy, and also needs to recharge also quite fast. Current lead acid batteries are still able to give the required boost, buts

fails in the regenerative braking phenomenon.

Thus lithium ion batteries are mostly proposed for the use in 42V technology. These batteries are currently in pro-

duction in non automotive applications, and have been tested for one million cycles of charging and discharging and al-

so have a good combination of specific energy and specific power. The downfall, however is the high cost incorporated.

Another battery being developed by Johnson controls laboratory is a 36V battery using a thin metal foil for lots of

power, while a reserve battery they are developing has a bulkier materials for capacity. In general terms of physical size,

the 36V battery will be bigger than a 12V battery as it would have 24 cells instead of 8. Using lightweight but similar

batteries currently used in motorsports will solve the problem.

3.6) Potential architectures

Whether the distribution is AC, DC or a mixture of both depends on the manufacturers’ individual choices and their

assumptions about cost, performance, manufacturability, controllability, repairability, adaptability and reliability.

Whatever the distribution architecture, it should be compatible with today's electrical 12V DC loads. This design will al-

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low present 12V infrastructure to be used while new, more efficient or functionally improved loads at other voltages

are introduced. As it is now, lamps and motors will account for most of the load. Incandescent lights will be continued

to powered on 12V be it AC or DC.

As for the wiring, it is still undecided as to what the industry standard would be.

The big question is that should it be a dual voltage dual battery type or a single voltage, single battery type. The

first one would offer both, 42V and 14V busses. The second will comprise of a 42V alternator, a 36V starter and bat-

tery. Each of these configurations has advantages and disadvantages. Each OEM will have its own philosophy and as-

sumptions. For example, GM aims to develop a dual voltage system and then transit it to a single voltage system. Con-

versely, BMW aims at a single voltage system.

3.6.1) Proposed architecture systems

Single 42V system

It is the simplest design on paper, but the most difficult one to implement. In the long term, however this would

avoid cost, weight and packaging problems created by 2 batteries. The assumption is that energy management system

would be smart enough to monitor a single battery and manage loads to prevent depleting the 36V battery to the point

where vehicle cannot be started. This is yet expensive initially and would be inappropriate for the manufacturer to

change over all their vehicles at once.

Dual alternator-dual voltage

It could be either of the following:

Dual alternator

DC to DC converter.

With this architecture, 42V bus would power the electrical loads that benefit directly from higher voltage while the

rest of the loads would remain on 14V.

Fig – 3.6.1 Proposed architecture

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Chapter 4 – Charging System


4 – Charging System

Requirements of a charging system. Dynamo: Principle of operation, construction and working. Regulators,

Combined current and voltage regulators, etc. Alternator: Principle of operation, Construction, working. Rectification

of AC to DC.

4.1) Introduction

The modern charging system hasn't changed much in over 40 years. It consists of the alternator, regulator (which

is usually mounted inside the alternator) and the interconnecting wiring.

The purpose of the charging system is to maintain the charge in the vehicle's battery, and to provide the main

source of electrical energy while the engine is running.

If the charging system stopped working, the battery's charge would soon be depleted, leaving the car with a "dead

battery." If the battery is weak and the alternator is not working, the engine may not have enough electrical current to

fire the spark plugs, so the engine will stop running.

4.2) Requirements of a Charging system

The current demands on a modern vehicle are tremendous. The charging system must answer to these demands

and also be able to charge the battery under all operating conditions.

The charging output should be constant voltage regardless of engine load or speed. In brief, the following are the

requirements of a charging system

1. Supply the current demand made by all loads.

2. Supply whatever charge current the battery demands.

3. Operate at idle speed.

4. Supply constant voltage under all conditions.

5. Have an efficient power to weight ratio.

6. Be reliable, quiet and have resistance to contamination.

7. Require low maintenance.

8. Provide an indication of correct operation

4.2.1) Vehicle electric loads

Loads on an alternator can be covered under three separate headings. These are continuous, prolonged and in-

termittent the charging system of a modern vehicle has to cope with high demands under varying load conditions.

Fig 4.2.1.1 shows the increase in alternator current demands over the years. Continuous loads are those which

need to be supplied continuously by the alternator, such as firing of spark plugs. Prolonged one is such as charging of

the battery, which is almost continuous except when battery is fully charged. Intermittent would be amenities such as

heated seat, windscreen wiper etc. as discussed earlier in Ch 3, load on vehicle has almost reached 2kW which is an

alarming figure owing to the increased demands on the alternator.

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Graph – 4.2.1.1 Current demands on alternator by time

4.3) Charging system basics

The three important blocks of a charging system are the generator, battery and the loads. There are 2 configura-

tions which are possible. They are shown in fig 4.3.1. when the alternator voltage is less than the battery (engine slow

or not running for example), the direction of current flow is from battery to the vehicle loads. The alternator diodes

prevent the current flowing into the alternator. When the alternator output is greater than the battery voltage, current

will flow from the alternator to the vehicle loads and the battery. Thus it is clear that alternator battery voltage needs

to be greater than the battery voltage at all times when the engine is running.

Fig – 4.3.1 Vehicle charging system

4.3.1) Charging voltages

The main consideration of the charging voltage is the battery terminal voltage when fully charged. If the charging

system voltage is set to this value, there can be no risk of overcharging the battery. This is knaown as the constant volt-

age charging technique. An amount of 14.2 ± 0.2V is the accepted charging voltage for a 12V system.

The other areas for consideration when determining the charging voltage are any expected voltage drops in the

charging circuit wiring and the operating temperature of the system and battery. The voltage drops must be kept mini-

mum, but it is important to note that the terminal voltage of alternator may be slightly above the nominal battery volt-

age.

4.4) The Dynamo or Generator

These were the original electrical generation units used on automobiles - it was much later on that alternators

were invented and car manufacturers switched over to them.

The generator is like an electric motor in reverse. Instead of applying electricity to it to make it spin, when you spin

it, it makes electricity. There are three parts of a generator:

Frame

Armature

Field coils

The generator produces electricity by spinning a series of windings of fine wire (called the armature) inside of a

fixed magnetic field by connecting them to a belt and pulley arrangement on the engine. As the armature is spun by the

rotation of the belt and pulley, it gets a current and voltage generated in those windings of wire. That current and volt-

age will be directly proportional to the speed that the armature spins and to the strength of the magnetic field. If you

spin it faster, it makes more and if you make the magnetic field stronger it makes more current. The speed of the spin-

ning is controlled by the speed of the engine - that's why you need to rev the engine up to help charge the battery fast-

er. The magnetic field is controlled by an electro-magnet, so by changing the amount of current supplied to the electro-

magnets that make up the field you control the strength of the magnetic field. This current is referred to as the "field"

current and it is controlled by the regulator in response to the electrical needs of the automobile at any given time.

The voltage of the generator is controlled by the number of windings in the armature. The current output is con-

trolled by the field current, but also by the speed at which the armature is spinning. This is important because a genera-

tor can only put out its maximum rated current at or above some speed - at lower speeds the output drops off very

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quickly. This is why a generator-equipped car will not charge (or even maintain!) the battery at idle and this is one of

the main reasons for the development of the alternator.

The current generated in the armature is AC - not DC. To get it converted to DC so it can charge the battery and run

the electric loads, a device called a commutator is used to "rectify" this situation. It is on the armature and has a series

of contacts along it's outer surface. Two spring-loaded brushes slide on the commutator - one brush is connected to

ground and the other is connected to the main output of the generator. As the armature and commutator assembly ro-

tates, the brushes come touch the different contacts on the commutator such that the polarity of the current moving in

the armature is always connected to the correct brushes. The net effect of this is that the generator output is always DC

even though the current inside the armature windings is always AC. A schematic diagram of the generator is as shown

in fig 4.4.1.1.

Fig – 4.4.1.1 Schematic diagram of the dynamo principle

4.5) Regulators

4.5.1) Voltage Regulator

In older electromechanical regulators, voltage regulation is easily accomplished by coiling the sensing wire to make

an electromagnet. The magnetic field produced by the voltage attracts a moving ferrous core held back under spring

tension or gravitational pull.

As the voltage increases, the magnetic field strength also increases, pulling the core towards the field and opening

a mechanical power switch.

As the voltage decreases, the spring tension or weight of the core causes the core to retract, closing the switch al-

lowing the power to flow once more.

If the mechanical regulator design is sensitive to small voltage fluctuations, the motion of the solenoid core can be

used to move a selector switch across a range of resistances or transformer windings to gradually step the output volt-

age up or down, or to rotate the position of a moving-coil AC regulator.

Early automobile generators and alternators had a mechanical voltage regulator using one, two, or three relays

and various resistors to stabilize the generator's output at slightly more than 6 or 12 V, independent of the engine's rpm

or the varying load on the vehicle's electrical system. Essentially, the relay(s) employed pulse width modulation to regu-

late the output of the generator, controlling the field current reaching the generator (or alternator) and in this way con-

trolling the output voltage produced.

The regulators used for generators (but not alternators) also disconnect the generator when it was not producing

electricity, thereby preventing the battery from discharging back through the stopped generator. The rectifier diodes in

an alternator automatically perform this function so that a specific relay is not required; this appreciably simplified the

regulator design. Fig 4.5.1.1 shows a voltage regulator.

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A current regulator also works on almost the same principle as a voltage regulator

Fig – 4.5.1.1 voltage regulator

4.5.2) Combined current and voltage regulators

A regulator consists of a series winding and a shunt winding both wound on a single core. The series winding is

made up of a few turns of thick wire, one end connected to the field terminal of the regulator and the other end

grounded via a contact point. The other winding is the shunt winding which is made up of a few turns of thin wire, one

end of which is connected to cutout relay and the other to the ground.

As shown in fig 4.5.2.1, a combined current and voltage regulator is made up of three basic parts, a voltage regula-

tor, a current regulator and a cutout relay. We shall discuss each part one by one as follows

Voltage regulator

The operation of the voltage regulator is same as the one explained above. When the generator produces a higher

voltage than required, and for which the regulator is set, the force due to the shunt and series winding will pull down

the armature, thereby breaking the contact points. Once this happens and the contact points are broken, the voltage

starts to reduce till a point is reached that the voltage through the windings is insufficient to hold the armature down

and again the contact is established due to spring action of the contact arm. This happens several times in one second

(around 200 times!) and the voltage is regulated by pulse width modulation.

Current regulator

The current regulator also works on somewhat the same principle of electromagnetic field generation. It consists

of a heavy series winding around a core. The contact points are closed and the generator field circuit is grounded. When

the load on the generator increases, the generator voltage is insufficient to operate the voltage regulator and current

continues to rise till a stage is reached when the current regulator coil is sufficient to pull the armature down separating

the contact points, thus inserting sufficient resistance for the generator output until the current decreases to an allow-

able value in which case, the current will fall and thus the winding will have insufficient energy to hold the armature

down. Contact is again made and current again starts to rise.

Cutout relay

When the generator speed is very low due to low engine speed, the output is not sufficient to balance the battery

voltage and the necessity to cutout the generator from the battery arises. This is because the battery would discharge

through the generator. The contact can again be made only when the engine has gained sufficient speed to match out-

put to the battery voltage. As shown, the cutout relay consists of 2 coils, shunt and series. When the generator is pro-

ducing sufficient voltage, the electromagnetic phenomena of both the windings is sufficient to support each other, the

electromagnet pulls down the armature and contact is established. However, when the generator is not producing

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enough output, the fields due to shunt and series winding oppose out, which causes the electromagnetic pull to weak-

en and the battery is cutoff from the circuit.

Fig – 4.5.2.1 Combined current and voltage regulator

4.5.3) Regulators drawbacks

A regulator as seen depends on electro mechanical principles. This has many inertial problems and also problems

related to hysteresis. Some of the problems associated with alternator is given below:

Noisy operation due to constantly moving parts.

High amount of wear of contact points.

Arcing at contact points, causing carbon to develop there.

Very fine adjustment of spring tension required for all the applications for particular output.

Change in elasticity of springs due to fatigue is common.

This leads to change in the regulated entity value, be it current, voltage or the cutout of the battery.

Due to these drawbacks, alternators are now preferred over dynamos because the semiconductor technology is

used better in conjunction with electronic voltage regulators.

4.5.4) Electronic regulators

The circuit diagram of such a regulator is as shown in Fig 4.5.4.1. When the alternator first increases in speed, the

output will be below the preset level. Under these circumstances the transistor T2 will be switched on by a feed to its

base by the resistor R3. This allows full field current to flow, thus increasing voltage output. When the preset voltage is

reached the zener diode will conduct. The resistances R1 and R2 are in simple series circuit to set the voltage appropri-

ate to the value of the diode, when the supply is say 14.2V. Once ZD conducts T1 will switch on and pull the base of T2 to

the ground. This switches T2 off and so field current is interrupted, causing output voltage to fall. This will cause ZD to

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stop conducting, T1 will switch off allowing T2 to switch back on and so the cycle will continue. D1 is used to absorb back

emf generated.

Fig – 4.5.4.1 Electronic voltage regulator

4.6) Alternators

4.6.1) Principle of operation

Alternators generate electricity by the same principle as DC generators, namely, when the magnetic field around a

conductor changes, a current is induced in the conductor. Typically, a rotating magnet called the rotor turns within a

stationary set of conductors wound in coils on an iron core, called the stator. The field cuts across the conductors, gen-

erating an electrical current, as the mechanical input causes the rotor to turn. However, after every half revolution,

there would be reverse in polarity of magnet, hence we get AC current.

The rotor (having a constant magnetic field driven a permanent magnet) will attempt to take such position that N

pole of the rotor is adjusted to S pole of the stator's magnetic field, and vice versa. This magneto-mechanical force will

drive rotor to follow rotating magnetic field in a synchronous manner.

The alternator thus produces 3 phase AC current. This is given to a rectifier bridge which converts this into DC cur-

rent which can then be supplied to the loads. Refer Fig 4.6.1 and 4.6.2 for schematic details.

Fig – 4.6.1 Alternator exploded view

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Fig – 4.6.2 Alternator principle in conjunction with rectification

4.6.2) Rectification from AC to DC

As discussed earlier, there needs to be a DC supply to run the vehicle loads and also to charge the battery. As an al-

ternator produces 3 phase AC voltage, it needs to be rectified to DC, the principle of operation is as described below.

Rectification basic block – a semiconductor diode and Half wave rectification

A diode is like an electronic valve which allows only one flow of direction of current and blocks the current if flow-

ing from other side. Using one diode, we can achieve half wave rectification. This means that only positive cycle appears

on the output, there is no negative side on the output. Refer fig 4.6.2.1.

Fig – 4.6.2.1 Half wave rectification

Full wave rectification

There are many ways to achieve this. The one using 2 diodes is shown here, in the positive half of input one diode

operates and other is redundant and in the negative half, the other diode operates and the former one, which was con-

ducting in the first half is now redundant.

Fig – 4.6.2.2 Full wave rectifier

Rectifier circuit of an automobile alternator

As seen above, 2 diodes produce full wave rectification of a single phase input. For three phase input, we thus re-

quire 6 diodes, along with a resistor bridge of star connection or delta connection. The circuit diagram for an alternator

is as shown in Fig 4.6.2.3, below.

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Fig – 4.6.2.3 Alternator circuit employing star connection

As seen above, there are 8 diodes for rectification. Usually, six diodes are sufficient but 2 extra diodes are put as

indicated which is given connection from star bridge common point to even rectify any voltage occurring due to an un-

balanced circuit. This increases the rectifier efficiency. 3 field diodes, one for each phase are used to give warning light

signals. There is a regulator which regulates the output, as discussed earlier. The slip rings and the field windings are

used to input to the regulator. There are 2 ways in which this is done. One way is to supply constant feed to the feed

windings from excitation diodes and regulator switches the earth side, the other system, one side of the field windings

is constantly earthed and the regulator switches the supply side.

Alternators do not require any current regulators. This is because if the output voltage 9s regulated, the voltage

supplied to the field windings cannot exceed the pre-set level. This in turn will only allow a certain current to flow due

to resistance of the winding, and hence limit is set for the field strength. Electronic voltage regulation is usually used in

modern cars using a Zener diode. This diode can be constructed to breakdown and conduct in reverse at a precise set

level.

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Chapter 5 Starting System


5 – Starting System

Requirements, Carious torque terms used. Starter motor drives : Bendix, folo through, Barrel, Rubber compres-

sion, Compression spring, Friction clutch, Overruning clutch, Dyer. Starter motor solenoids and switches, Glow plugs.

The "starting system", the heart of the electrical system in your car, begins with the Battery. The key is inserted in-

to the Ignition Switch and then turned to the start position. A small amount of current then passes through the Neutral

Safety Switch to a Starter Relay or Starter Solenoid which allows high current to flow through the Battery Cables to the

Starter Motor. The starter motor then cranks the engine so that the piston, moving downward, can create a suction

that will draw a Fuel/Air mixture into the cylinder, where a spark created by the Ignition System will ignite this mixture.

If the Compression in the engine is high enough and all this happens at the right Time, the engine will start.

5.1) Engine starting requirements

An IC engine requires the following in order to start and then continue in operation

Combustible mixture

Compression stroke

A form of ignition (by spark plug in SI engine and by Glow plug during the time of starting for CI engine)

Minimum starting speed (approx 100 rpm)

In order to produce the first three of these, a minimum rpm of 100 is necessary, that is the fourth condition. This is

where the electric starter comes in. the ability to reach this minimum speed is again dependant of the following factors

Rated voltage of the starting system.

Lowest possible temperature at which the system must function. This is known as starting limit temperature.

Engine cranking torque. In other words the torque that has to be applied to start the engine.

Battery characteristics.

Voltage drop between battery and starter.

Starter to ring gear ratio.

Characteristics of the starter.

Minimum cranking speed of the engine at starting limit temperature.

Fig 5.1.1 shows the basic diagram of the engine starting system in conjunction with the other electric systems of a

car.

Fig – 5.1.1 electrical system of a car

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Chapter 5 – Starting system


5.2) Various Torque terms used with engine starting

There is basic 2 torques associated with engine starting. One is the starter torque and other is the engine torque. It

must be noted that engine torque here is related to the amount of torque required for the engine to crank and thus

eventually start. For passenger cars starter torque of 10 to 30 Nm is employed, and for heavy vehicles it is in the range

50 to 100 Nm. The starter torque and the engine torque vary considerably with temperature. This is shown by graph

5.2.1 below.

Graph – 5.2.1 engine rpm vs required torque wrt torques.

Typical starting limit temperatures are usually quoted by manufacturers at -20oC and +20oC and torque values are

mentioned. Starting limit temperatures for typical vehicles are as follows:

-18oC to -25oC for passenger cars.

-15oC to -20oC for trucks and busses.

5.3) Starting motor

The starting motor, also called the starter motor, is driven by means of the current taken from the battery. It is

usually mounted on the side of the engine on the flywheel end.

As the starter motor needs to deliver heavy torque, it is series wound, such that the field coils are connected in se-

ries to the armature and hence the current in them is equal. However, present day, some motors are series-shunt

wound. The advantage of this type is the lower internal resistance which decreases the current demand for a given

starting torque.

The construction of starter motor is similar to a DC generator with the exception that DC generator is series

wound. The main components are:

Body

Armature

Commutator

Field windings

4 field poles and 4 brushes

The brushes are held in contact with the Commutator by means of brushes. At the end of armature shaft there is a

‘starter motor drive mechanism’ (explained in next section) which drives the engine.

5.4) Starting motor drives

For starting the engine, as said above, the speed of an engine should be at 100 rpm during cranking. If a motor giv-

ing 1500 rpm is used with a pinion to flywheel gear reduction of 15:1 would be sufficient. However, when the engine

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starts, the pinion will move at a tremendous speed at 15 times the speed of the engine. This will cause the commutator

brushes etc to fly away by the centrifugal force. For this reason a mechanism for disengagement of the pinion once the

engine starts is essential. These mechanisms are referred to as starting motor drives. They are of the following types:

Bendix Drive: these are inertia type drives. They are of 4 different types viz standard bendix drive, ‘Folo-thru’ drive. Compression spring type bendix drive and rubber spring type bendix drive

Pre engaged type of drives: these consist of Overruning clutch type drive and Dyer drive.

5.4.1) Standard bendix drive

Refer to Fig 5.4.1.1 for a detailed diagram. The inertia type of starter motor employing standard bendix drive has

been the technique used for over 85 years, but it is now becoming redundant. There is a threaded sleeve on the arma-

ture shaft. The sleeve can slide or turn freely on the armature shaft. The shaft is keyed to a fixed drive head which is

connected torsionally to a sliding dog. This takes on shock of engagement and disengagement. On the sleeve there is a

pinion which is attached to an unbalance weight to prevent rotation of pinion on sleeve threads. When starter motor

runs, the pinion remains still due to its inertia and, because of the screwed sleeve rotating inside it, the pinion is moved

into mesh with the ring gear.

When the engine fires and runs under its own power the pinion is driven faster than the armature shaft. This caus-

es the pinion to be screwed back along the sleeve and out of engagement with the flywheel. The main spring acts as a

buffer when the pinion first takes up the driving torque and also acts as a buffer when the engine throws the pinion

back out of mesh

Fig – 5.4.1.1 – Standard Bendix drive

5.4.2) ‘Folo thru’ drive

This is similar in construction to the standard bendix drive. The armature shaft is connected to a threaded sleeve

through a spring and an overrunning clutch. The inside of the pinion barrel fits into the sleeve thread. Towards the end

of the sleeve is provided a detent as shown (Fig 5.4.2.1) two spring loaded pins viz the lock pin and the anti drift pin are

also provided. The anti drift pin provides only frictional contact with the sleeve teeth, whereas the lock pin in conjunc-

tion woth the detent is as further explained below.

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Fig – 5.4.2.1 – Folo thru drive

The engagement of the pinion and the flywheel takes place in a similar way as explained above for bendix drive.

However towards the end of the pinion travel the lockpin drops into the detent and would not let the pinion disengage

prematurely due to a false start such as premature firing. The pinion thus continues travelling the flywheel till the en-

gine gets really started. When the engine reaches about 400 rpm the lockpin comes out of the detent due to centrifugal

force. Then again the pinion disengages as in a standard bendix drive.

The anti drift pin is loaded with a spring stiffer than a lock pin. This prevents the drifting of the pinion and engaging

with the flywheel accidently. The overrunning clutch acts as an added safety device so that if for any case the pinion

does not disengage, the clutch would prevent damage to the motor.

5.4.3) Compression type bendix drive

This differs from a direct bendix drive that the threaded sleeve is mounted directly on the splined armature shaft.

A spring under compression is employed in between the sleeve and the nut which is fixed on between the pinion and

the collar on the shaft.

When the motor is started, the sleeve starts rotating along with the armature shaft. This causes the pinion to travel

towards the motor till its teeth engage completely with the flywheel gear. By this time the pinion also strikes against

the collar which prevents further pinion travel. The spring on the sleeve over which the pinion moves serves to avoid

shock due to striking of pinion with collar. The pinion therefore tries to rotate but is offered initial resistance by the fly-

wheel which is stationary. The torque of the shaft then has a tendency to force the threaded sleeve further out against

the spring tension, till the flywheel starts rotating. The spring tension is then consequently relieved when the engine

fires as it meshes out the pinion then. This type of drive is as shown in Fig 5.4.3.1.

Fig – 5.4.3.1 – Compression spring bendix drive

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5.4.4) Rubber spring bendix drive

This is similar to compression spring bendix drive with the only difference being that the compression spring is re-

placed by a rubber spring. This is done to avoid the damage which is caused when due to false engine starting the pin-

ion gets disengaged and attempt is made to bring it back into mesh.

5.4.5) Overrunning clutch type drive or pre engaged starter

Figure 5.4.5.1 shows a schematic figure of the circuit. Pre-engaged starters are fitted to the majority of vehicles in

use today. They provide a positive engagement with the ring gear, as full power is not applied until the pinion is fully in

mesh. They prevent premature ejection as the pinion is held into mesh by the action of a solenoid. A one-way clutch is

incorporated into the pinion to prevent the starter motor being driven by the engine. An example of a pre-engaged

starter in common use is shown in the Figure the next figure shows the circuit associated with operating this type of

pre-engaged starter. The basic operation of the pre-engaged starter is as follows.

When the key switch is operated a supply is made to the solenoid. This causes two windings to be energized, the

hold-on winding and the pull-in winding. Note that the pull-in winding is of very low resistance and hence a high current

flows. This winding is connected in series with the motor circuit and the current flowing will allow the motor to rotate

slowly to facilitate engagement.

At the same time the magnetism created in the solenoid attracts the plunger and via an operating lever pushes the

pinion into mesh with the flywheel ring gear. When the pinion is fully in mesh the plunger at the end of its travel causes

a heavy-duty set of copper contacts to close. These contacts now supply full battery power to the main circuit of the

starter motor. When the main contacts are closed the pull-in winding is effectively switched off due to equal voltage

supply on both ends. The hold-on winding holds the plunger in position as long as the solenoid is supplied from the key

switch.

When the engine starts and the key is released, the main supply is removed and the plunger and pinion return to

their rest positions under spring tension. A lost motion spring located on the plunger ensures that the main contacts

open before the pinion is retracted from mesh.

During engagement if the teeth of the pinion hit the teeth of the flywheel (tooth to tooth abutment), the main

contacts are allowed to close due to the engagement spring being compressed. This allows the motor to rotate under

power and the pinion will slip into mesh.

The torque developed by the starter is passed through a one-way clutch to the ring gear. The purpose of this free-

wheeling device is to prevent the starter being driven at excessively high speed if the pinion is held in mesh after the

engine has started. The clutch consists of a driving and driven member with several rollers in between the two. The

rollers are spring loaded and either wedge-lock the two members together by being compressed against the springs or

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Fig – 5.4.5.1 – Pre engaged starter.

5.4.6) Dyer Drive

This type of drive is most suitable for heavy engines. It is so designed that the engagement of the pinion with the

flywheel gear takes place before starter motor switch is operated. This avoids possibility of gear damage.

The main components of a dyer drive are as shown in fig 5.4.6.1. the shift sleeve is free to move on the armature

shaft, in which are provided the spiral teeth. The shift sleeve is operated by means of a shift lever. The snug on the pin-

ion guide fits into the slot of the pinion, which has internal splines corresponding to armature shaft splines. However,

the pinion fits on the armature shaft rather loosely.

When the shift lever is pressed, the shift sleeve is pushed to the right and consequently the pinion is also moved in

that direction. However, because of the spiral teeth, there is angular motion also. With the further pushing of the shift

lever the pinion thus gets engaged with the flywheel. However the chances are that the teeth are not aligned in this po-

sition. In this case the shift sleeve continues to move the pinion guide along the armature shaft, which because of the

snug fitting on the shaft rotates without any linear motion, taking the pinion with it, till teeth are in mesh. Once mesh-

ing occurs, the further travel of shift lever switches the motor on.

Once the motor starts, the sleeve is immediately rotated back in its initial position. The disengagement takes place

on the starting of the engine as in case of bendix drive.

Fig – 5.4.6.1 – Dyer drive

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5.5) Starter motor solenoids

A relay is a device that allows a small amount of electrical current to control a large amount of current. A car start-

er motor uses a relay to solve the problem that a car has in needing a large amount of current to start the engine. A

starter relay is installed in series between the battery and the starter. Some cars use a starter solenoid (as shown here)

to accomplish the same purpose of allowing a small amount of current from the ignition switch to control a high current

flow from the battery to the starter.

Fig 5.5.1 Starter motor solenoid principle.

5.6) Glow plug

A glow plug is a pencil-shaped piece of metal with a heating element at the tip; that heating element, when electri-

fied, heats due to electrical resistance and begins to emit light in the visible spectrum (hence the term "glow" plug; the

effect is very similar to that of a toaster. The heat generated by the glow plugs is directed into the cylinders, and serves

to warm the of the engine block immediately surrounding the cylinders. This aids in reducing the amount of thermal dif-

fusion which will occur when the engine attempts to start.

The use of a glow plug is only in diesel engines. The reason is that diesel engines rely solely on compression. The

piston rises, compressing the air in the cylinder; this, by natural effect, causes the air's temperature to rise. By the time

the cylinder reaches the top of its travel path, the temperature in the cylinder is very high. The fuel mist is then sprayed

into the cylinder; it instantly combusts, forcing the piston downwards, thus generating power. The pressure required to

heat the air to that temperature, however, necessitates the use of a large and very strong engine block. The problem

posed is that in cold weather, if the engine has not been running (as is the case when the car is left to sit overnight),

that large engine block becomes very cold; when one then attempts to start the engine, the cold engine block acts as a

heat sink, quickly dissipating the heat generated by the pistons compressing air. The engine is then unable to start, be-

cause it cannot generate and maintain enough heat for the fuel to ignite. Thus glow plug generates this heat for the

starting of the engine.

Fig 5.6.1) A Glow plug (tip on the right)

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Chapter 6 – Ignition system


6 – Ignition systems

Capacitor Discharge Ignition System, Distributor less ignition system, direct ignition system. Hall effect pulse

generator, Inductive pulse generator, Constant dwell system, constant energy system.

6.1) Fundamentals

6.1.1) Functional requirements

The main function of the ignition system is to give spark to the engine inside the combustion chamber at the end

of the compression stroke, to ignite the A/F mixture in SI engines.

For a spark to jump across a gap of 0.6mm under normal atmospheric conditions, a voltage of 2-3 kV is required.

For a spark to jump a similar gap inside the combustion chamber, where the pressure is 8 times the pressure of the at-

mosphere, the same voltage required is 8kV. As compression ratio increases, so does the spark voltage requirement.

Also, the system has to deliver this voltage at the precisely right time in the right cylinder. It also has to vary the

time of spark according to engine load and speed characteristics.

6.1.2) Components of conventional ignition system

The various components of a conventional ignition system is as described below. It is shown graphically in fig

6.1.2.1.

NOTE:> the important components are given in detail at the end of the chapter.

Spark plug

A spark plug is an electrical device that fits into the cylinder head of SI engines and ignites compressed A/F mixture

by means of an electric spark. Spark plugs have an insulated center electrode which is connected by a heavily insulated

wire to an ignition coil or magneto circuit on the outside, forming, with a grounded terminal on the base of the plug, a

spark gap inside the cylinder.

A spark plug is composed of a shell, insulator and the conductor. It pierces the wall of the combustion chamber

and therefore must also seal the combustion chamber against high pressures and temperatures, without deteriorating

over long periods of time and extended use.

Ignition switch

An ignition switch is a key operated switch which switches the ignition circuit on and off.

Ballast resistor

It is shorted out during the starting phase to cause a more severe spark. Also contributes towards improving spark

at higher speeds.

Contact breakers

Switches the primary ignition circuit on and off the charge and discharge the coil.

Capacitor

Suppresses arcing by storing charge in it, this allows rapid brake of primary current and hence a rapid collapse of

coil magnetism, which produces higher voltage output.

HT distributor

Directs spark from the coil to each cylinder in a pre sequence.

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Centrifugal advance

Changes the ignition timing with engine speed. As speed increases, timing is advanced.

Vacuum advance

Changes valve timing depending on the engine load. On conventional systems the vacuum advance is the most

crucial during cruising conditions.

Ignition coil

It is an induction coil in an automobile's ignition system which transforms the battery's 12 volts (6 volts in some

older vehicles) to the thousands of volts needed to spark the spark plugs.

This is done by transformer action. 2 wires are wound around a common core, the primary coil and the secondary

coil. The secondary coil is made up of a large number of high tension cable windings on the core. The primary coil is

made up of a small number of windings of low tension wire. When electricity from battery (or alternator) excites the

primary winding, correspondingly high voltage is induced in the secondary winding, which gives the spark to the spark

plugs. A figure of an ignition coil is as show in in fig 6.1.2.1.

Fig – 6.1.2.1conventional ignition system

6.2) Capacitor discharge ignition

CDI ignition is most widely used today on automotive and marine engines. A CDI module has "capacitor" storage of

its own and sends a short high voltage (about 250+ volts) pulse through the coil. The coil now acts more like a trans-

former (instead of a storage inductor) and multiplies this voltage even higher. Modern CDI coils step up the voltage

about 100:1. So, a typical 250v CDI module output is stepped up to over 25,000v output from the coil. The CDI output

voltage of course can be higher. So you'll see CDI systems claiming coil output capability over 40,000-60,000 volts!!? As

you will see this is not exactly what happens at the plug but for theoretically this works out. The huge advantage of CDI

is the higher coil output and "hotter" spark. The spark duration is much shorter (about 10-12 microseconds) and accu-

rate. This is better at high RPM but can be a problem for both starting and/or lean mixture/high compression situations.

CDI systems can and do use "low" resistance coils.

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Fig – 6.2.1 – CDI system

6.3) Distributor less Ignition system

The spark plugs are fired directly from the coils. The spark timing is controlled by an Ignition Control Unit (ICU) and

the Engine Control Unit (ECU). The distributor less ignition system may have one coil per cylinder, or one coil for each

pair of cylinders.

Some popular systems use one ignition coil per two cylinders. This type of system is often known as the waste

spark distribution method. In this system, each cylinder is paired with the cylinder opposite it in the firing order (usual-

ly 1-4, 2-3 on 4-cylinder engines or 1-4, 2-5, 3-6 on V6 engines). The ends of each coil secondary leads are attached to

spark plugs for the paired opposites. These two plugs are on companion cylinders, cylinders that are at Top Dead Center

(TDC) at the same time. But, they are paired opposites, because they are always at opposing ends of the 4 stroke engine

cycle. When one is at TDC of the compression stroke, the other is at TDC of the exhaust stroke. The one that is on com-

pression is said to be the event cylinder and one on the exhaust stroke, the waste cylinder. When the coil discharges,

both plugs fire at the same time to complete the series circuit.

Since the polarity of the primary and the secondary windings are fixed, one plug always fires in a forward direction

and the other in reverse. This is different than a conventional system firing all plugs the same direction each time. Be-

cause of the demand for additional energy; the coil design, saturation time and primary current flow are also different.

This redesign of the system allows higher energy to be available from the distributorless coils, greater than 40 kilovolts

at all rpm ranges.

The distributorless Ignition System (DIS) uses either a magnetic crankshaft sensor, camshaft position sensor, or

both, to determine crankshaft position and engine speed. This signal is sent to the ignition control module or engine

control module which then energizes the appropriate coil.

The advantages of no distributor, in theory, is:

No timing adjustments

No distributor cap and rotor

No moving parts to wear out

No distributor to accumulate moisture and cause starting problems

No distributor to drive thus providing less engine drag

The major components of a distributorless ignition are:

ECU or Engine Control Unit

ICU or Ignition Control Unit

Magnetic Triggering Device such as the Crankshaft Position Sensor and the Camshaft Position Sensor

Coil Packs

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Fig – 6.3.1 – Direct Ignition system

6.3) Direct Ignition system

This is just an extension of the above distributorless ignition system. This system utilizes one induction coil for each

cylinder. These coils are mounted directly on the spark plugs. An individual coil for each spark plug makes sure that the

rise time for the low inductance primary winding is very fast.

An important addition in this is the presence of a camshaft sensor to detect as to which cylinder is on the compres-

sion stroke. The Fig 6.3.1 would hold true for the direct ignition systems if every coil is connected to only one spark

plug, and the other end grounded.

6.4) Hall effect pulse generator

The Hall effect refers to the potential difference (Hall voltage) on the opposite sides of an electrical conductor

through which an electric current is flowing, created by a magnetic field applied perpendicular to the current 9see fig

6.4.1)

As the central shaft of the distributor rotates, the vanes attached under the rotor arm alternatively cover and un-

cover the hall chip. The number of vanes corresponds to number of cylinders. In constant dwell systems, the dwell is

determined by the width of the vanes. The vanes cause the hall chip to be alternatively in and out of the magnetic field.

The result is that the device will produce almost a square wave output, which can easily be used to switch other elec-

tronic circuits. There are 3 terminals on the component. +, – and 0. + and – are used for voltage supply and 0 is for out-

put voltage.

Typically the output of such a sensor is between 0-7 V. The operation of the hall effect pulse generator is as shown

in fig 6.4.2.

Fig – 6.4.1 – Principle of hall effect

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Fig – 6.4.2 – Hall effect pulse generator and output wave

6.5) Inductive pulse generator

These use the principle of electromagnetic induction to produce a signal. It is schematically as shown in fig 6.5.1.

many forms exist but all are based around a coil of wire and permanent magnets.

The rotating member is referred to as the relucator and as it rotates, there is a variation of the magnetic flux inter-

acting with the coil. The number of peaks per cycle depends on the number of cylinders.

Fig – 6.5.1 – Inductive pulse generator.

6.6) Constant Dwell system

Dwell is measured as an angle: with contact ignition, the points gap determines the dwell angle. The definition of

contact ignition dwell is: 'the number of degrees of distributor rotation with the contacts closed'.

Basically, dwell when applied to an ignition is a measure of the time during which the ignition coil is ‘charging.’ In

other words it is the time for which the current is flowing through the primary coil. The above definition, though holds

true, but nowadays it is described as a percentage of a charge-discharge cycle.

One example of the constant dwell system is the Lucas OPUS (Oscillating Pickup system). It consists of a timing ro-

tor, in the form of a plastic drum with a ferrite rod on each cylinder embedded around its edge. This rotor is mounted

on a shaft of a distributor. Another part of the system is the ‘pickup’ which is mounted on the base plate and comprises

of an E shaped ferrite core with primary and secondary windings enclosed in a plastic case. Three wires are connected

from the pickup to the amplifier. The amplifier contains an oscillator to energize the primary pickup winding, a

smoothed circuit and a power switching stage.

The mode of operation of this system is that the oscillator supplies a 450 kHz AC signal to the pickup primary wind-

ing. When one of the ferrite rod is in proximity to the pickup, the power transistor allows primary ignition to flow. As

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the distributor rotates, the ferrite rod passes the pickup and the magnetic linkage allows an output from the pickup

secondary winding. Via a smoothing stage and the power stage, the ignition coil will now switch off, producing a spark.

The drawback of the system was that at higher engine speeds, the time available to charge the coil was insufficient

which resulted in poor quality spark.

6.7) Constant energy systems

Constant energy means that, within limits, the energy available to the spark plug remains constant under all work-

ing conditions.

The basis of this system is that the dwell must increase with the increase in engine speed. This will only benefit if

the ignition coil can be charged to its full capacity in a smaller time, i.e. the time available for the maximum dwell at the

highest possible engine speed. The constant energy coils are very low resistance and low inductance. Typical resistance

is less than 1 ohm.

Due to the high nature of constant energy ignition coils, the coil cannot be allowed to be switched on for more

than a certain time. This is not a problem when engine is running at variable dwell or current limiting circuits which lim-

its coil overheating. Some form of protection must be provided for when the ignition is on but engine is not running.

This is called the ‘stationary engine primary current cutoff’

An energy value of 0.3 mJ is required to ignite a static stoichiometric ratio. In some conditions, the need rises to 3-

4 mJ. This has made constant energy almost essential for all today's vehicle to meet the stringent emission norms.

Fig – 6.7.1 Constant energy systems

6.7) Spark plug details

Construction

Refer fig 6.7.1 for constructional details.

Terminal: The top of the spark plug contains a terminal to connect to the ignition system

Ribs: the physical shape of the ribs functions to improve the electrical insulation and prevent electrical energy from leaking along the insulator surface from the terminal to the metal case.

Insulator: The insulator is typically made from an aluminium oxide ceramic and is designed to withstand 650 °C and 60,000 V[citation needed

Seals: the seals ensure there is no leakage from the combustion chamber

Metal case: The metal case (or the "jacket" as many people call it) of the spark plug bears the torque of tightening the plug, serves to remove heat from the insulator and pass it on to the cylinder head, and acts as the ground for the sparks passing through the center electrode to the side electrode.

Insulator tip: The tip of the insulator surrounding the center electrode is within the combustion chamber and directly affects the spark plug performance, particularly the heat range.

Side electrode, or ground electrode: The side electrode is made from high nickel steel and is welded to the side of the metal case

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Heat Range

A spark plug is said to be "hot" if it is a better heat insulator, keeping more heat in the tip of the spark plug. A spark

plug is said to be "cold" if it can conduct more heat out of the spark plug tip and lower the tip's temperature. Whether a

spark plug is "hot" or "cold" is known as the heat range of the spark plug. The heat range of a spark plug is typically

specified as a number, with some manufacturers using ascending numbers for hotter plugs and others doing the oppo-

site, using ascending numbers for colder plugs.

Fig – 6.7.1 Spark plug constructional details

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Chapter 7 – Wiring


7 – Wiring

Cables, sizes, colours, codes, connectors. Multiplex wiring system, Wiring harness system, CAN system

7.1) Electrical cables

7.1.1) Cable sizes

Cables used for automobile are always copper strands insulated with PVC. Copper beside its low resistivity of about

1.7x10-8 Ωm has ideal properties such as ductility and malleability. Moreover, PVC on the other hand has a resistivity of

1015 Ωm but is also resistant to all automobile oils and fuels (except battery electrolyte).

The size of the cable used determines the current drawn by the consumer. Larger cables means smaller voltage

drop in the circuit but higher the diameter. thus a trade off is necessary.

It is designated by a number X Y. X designates number of strands, and Y designates diameter in mm. For example,

15 0.3 indicates, 15 strands of 0.3mm diameter wire.

7.1.2) Cable colours

There are several colour codes used by different manufacturers and different legislative standards. They are yet to

be standardized globally. The colour codes as per British standards are given in table 7.1.2.1.

Colour Use

Brown Main battery feed

Blue Head light

Red Sidelight

Green Ignition controlled fuel supply

Black Earth

orange Wiper

Slate

Light green Instruments

Table – 7.1.2.1 British standard colour codes

7.1.3) Connectors

Terminals need to be of high quality creating as little blockage to flow of current. They ought to be water proof,

and loose enough to remove, put back, and tight enough to be in contact in daily use under severe conditions of vibra-

tions.

Protection against corrosion is done in two ways, one by applying water repelling grease on the terminal and other

is by manufacturing a suitable rubber seal. Many a times, both are used in conjunction as well.

Circular multipin connectors are used in many cases with pins varying from sizes of 1mm to even 5mm. The thing

to be most careful is that the connections go where they are supposed to go. Thus special male female connectors for

different applications are incorporated with full proofing against faulty connections. This means that one plug shall only

fit into one socket in the vicinity, and thus cross connection is avoided. Various types of connections are shown in fig

7.1.2.1.

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Fig – 7.1.2.1 – Different connections used in cars

7.2) Wiring harness system

The vehicle harness system has developed over the years from a loom containing just a few wires, and to looms

used at present in top of the range vehicles, containing as much as 1000 separate wires. Modern vehicles have wiring

harness constructed in a number of ways, which are given as follows:

Bundle of wires wrapped in non adhesive PVC tape. The tape is non adhesive as it gives flexibility to the bundle of wires

Place the cables side by side and plastic weld them. This makes it flat, which causes the cables to run through thin sec-tions such as under the carpets etc.

The wires are placed in tubes of contours designed as per shape of the car. It makes the harness design waterproof and also makes it better sealing.

Requirements

1. Cables must be as short as possible

2. The loom must be protected against physical damage.

3. Number of connections must be as low as possible.

4. Modular design may be appropriate

5. Accident damage areas need consideration

6. Production line techniques must be established

7. Access must be possible to the main components

Usually, the various systems are clubbed together and one plug-socket assembly is incorporated. The number of

connections cannot be practically kept low, as then after sales repair become impossible. For example, the entire in-

strument cluster in all cars has only one plug containing as much as 50 connections!!

Due to the high number of wiring looms in the cars, they are clubbed together and divided into more manageable

sub-assemblies. The overall layout of the loom may be ‘E’ type or an ‘H’ type as shown in the fig 7.2.1.

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Fig – 7.2.1 E type and H type wiring Harness system

7.3) Multiplex wiring system

7.3.1) Limitation of conventional wiring system

The complexity of modern wiring systems has been increasing steadily over the last twenty-five years or so and re-

cently has increased dramatically. It has now reached a point where the size and weight of the wiring harness is a major

problem. The number of separate wires required on a top of the range vehicle can be in the region of 1200. The wiring

loom required to control all functions in or from the driver’s door can require up to 50 wires, the systems in the dash-

board area alone can use over 100 wires and connections. This is clearly becoming a problem as apart from the obvious

issue of size and weight, the number of connections and number of wires increase the possibility of faults developing. It

has been estimated that the complexity of the vehicle wiring system doubles every 10 years.

The number of systems controlled by electronics is continually increasing. A number of these are already in com-

mon use and the others are becoming more widely adopted. Some examples of these systems are listed below.

Engine management

Stability control

Anti-lock brakes

Transmission management

Active suspension

Communications and multimedia.

All the systems listed above work in their own right but are also linked to each other. Many of the sensors that

provide inputs to one electronic control unit are common to all or some of the others. One solution to this is to use one

computer to control all systems. This however would be very expensive to produce in small numbers.

A second solution is to use a common data bus. This would allow communication between modules and would

make the information from the various vehicle sensors available to all of them.

7.3.2) Multiplex data bus

In order to transmit different data on the line, a number of criteria must be carefully designed and agreed. This is

known as communications protocol. Some of the variables defined are as follows

1. Method of addressing

2. Transmission sequence

3. Control signals

4. Error detection

5. Error treatment

6. Speed or rate of transmission

The physical layer must be designed and agreed. This includes the following:

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Transmission medium: e.g. copper wire, fiber optics etc

Type of transmission coding: analogue or digital

Type of signals: voltage, current or frequency etc

The circuit to meet this criterion is called the bus interface and will often take the form of a single integrated cir-

cuit.

7.4) Controller Area Network (CAN)

Bosch has developed the protocol known as CAN or controller area network. This system is claimed to meet practi-

cally all requirements with a very small chip surface (easy to manufacture and, therefore, cheaper). CAN is suitable for

transmitting data in the area of drive line components, chassis components and mobile communications. It is a compact

system, which will make it practical for use in many areas. Two variations on the physical layer are available which suit

different transmission rates. One for data transmission of between 100 K and 1 M baud (bits per second), to be used for

rapid control devices. The other will transmit between 10 K and 100 K baud as a low speed bus for simple switching and

control operations.

CAN modules are today developed by manufacturers such as Intel and Motorola. All modules are based on the

same CAN protocol. It is expected that this module will be standardized by the International Standards Organization

(ISO).

Many sensors and actuators are not ‘busable’ i.e. they cannot be used in the bus format. Thus conventional wiring

system will not be replaced completely. Fig 7.4.1 shows the CAN bus system layout.

Fig – 7.4.1 CAN system layout

7.4.1) CAN System Signal

The CAN message signal consists of a sequence of binary digits (bits). Voltage (or light fiber optics) present indi-

cates the value ‘1’; none present indicates ‘0’. The actual message can vary between 44 and 108 bits in length. This is

made up of a start bit, name, control bits, the data itself, a cyclic redundancy check (CRC) for error detection, a confir-

mation signal and finally a number of stop bits. Fig 7.4.1.1 shows a schematic figure of CAN signal.

The name portion of the signal identifies the message destination and also its priority. As the transmitter puts a

message on the bus it also reads the name back from the bus. If the name is not the same as the one it sent then an-

other transmitter must be in operation which has a higher priority. If this is the case it will stop transmission of its own

message. This is very important in the case of motor vehicle data transmission.

All messages are sent to all units and each unit makes the decision whether the message should be acted upon or

not. This means that further systems can be added to the bus at any time and can make use of data on the bus without

affecting any of the other systems.

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Errors in the message are recognized by the cyclic redundancy check (CRC). This is achieved by arranging all the

numbers in the message into a complex algorithm.

I II 7 0 to

8x8

15 3 7

Start Name Control Data CRC

test

Confirmation End

Fig – 7.4.2 CAN signal format – The entire length of the signal is 44 to 108 bits

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Chapter 8 – Electronic Engine Controls


8 – Electronic Engine Controls

Electronic control module (ECM), operating modes of ECM (closed loop and open loop), inputs and output signals

from ECM. Electronic spark timing, Electronic spark control, Air management system, Idle speed control.

8.1) Electronic Control Module (ECM)

In automotive electronics, an electronic control module (ECM), also called a control unit or control module is an

embedded system that controls one or more of the electrical subsystems in a vehicle. Some of which are as mentioned.

Engine Control Unit, now even referred to as a Powertrain Control Module (PCM). This is explained in detail below.

Transmission Control Unit (TCU): This is common in automatic transmission which facilitates gear changes and various gear ratios in automatic/semi-automatic transmission system.

Telephone Control Unit (TCU): deals with telematics and telemetry (see chapter 12).

Man Machine Interface (MMI): Deals with the ergonomical aspects of the vehicle.

Door Control unit: deals with aspects such as door locking, child safe door locking etc.

Seat Control Unit: deals with automatic seat positioning as per driver needs in case of multiple driver driven vehicle (one car may be driven by more than one people; car remembers this and adjusts driver seat accordingly). It also in-cludes seat belt warning system etc.

Climate Control Unit: adjusts the climate inside the car in context to temperature and humidity. Controls operation of air conditioner and car heater in conjunction to the set value.

Of these, some are of more importance than the others. In the following articles, and even following chapters,

these shall be dealt with in detail

Engine control Unit (ECU)

An engine control unit (ECU) is an electronic control unit which controls various aspects of an internal combustion

engines operation. The simplest ECUs control only the quantity of fuel injected into each cylinder each engine cycle.

More advanced ECUs found on most modern cars also control the ignition timing, variable valve timing (VVT), the level

of boost maintained by the turbocharger (in turbocharged cars), and control other peripherals.

ECUs determine the quantity of fuel, ignition timing and other parameters by monitoring the engine through sen-

sors. These can include, MAP sensor, throttle position sensor, air temperature sensor, oxygen sensor and many others.

Often this is done using a control loop.

Before ECUs most engine parameters were fixed. The quantity of fuel per cylinder per engine cycle was deter-

mined by a carburetor or injector pump.

8.1.1) Operating modes

There are 2 main types of operating modes of the ECM. One is open loop and other is closed loop. As the name

suggests, closed loop systems are more adaptive than open loop system because of the simple fact that there is a dy-

namic behavior in the operation which makes it all the more reliable. They are explained below with suitable examples

Open loop

In this case, there is no feedback loop back to the input of the electronic control unit. An example of this system is

cruise control. In this case, the car can cruise at a set speed without the driver having to press the accelerator pedal.

The ECM shall monitor the car speed with the set speed, and in turn make changes in the engine intake parameters

such as air mass, air pressure, fuel mass, fuel pressure etc and vary these parameters to maintain the 2 values of rec-

orded speed and set speed in close allowable tolerances.

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Closed loop

The closed loop function incorporates a feedback loop which monitors and evaluates performance of the system

not only with the standard set values but also with the dynamic values that are recorded in conjunction with the out-

put. An example of this kind of a system is Adaptable cruise control. Not only does the ECM measure the speed of the

car and compare with the set speed. It also senses the distance of the car ahead of you and even slows the car down to

maintain a safe distance.

8.1.2) Terminologies associated with ECM

In the ECM, there are various terminologies associated. We shall discuss the terms used in conjunction to the ECU

as it is the most important aspect of the ECM.

ECU Algorithm

An ECU algorithm is a complex set of instructions based on which the ECU works. It is a set of instructions which

gives the exact detail of the way the ECU should act in all possible engine situations. A complex ECU shall have an algo-

rithm that if printed can take thousands of pages! Its complexity is magnified by the fact that there are more inputs and

more outputs to the ECU day by day as is seen in newer high end cars. An ECU algorithm takes care of each and every

input to the ECU, and how is the ECU supposed to act, i.e. which outputs to give to the actuators is stored in the algo-

rithms. These are locked and in most cases are a deal of high amount of confidentiality of companies.

Engine maps

Engine maps are a set of graphs on which an engine works. The task of the ECU algorithm is to make sure that the

operating point of the engine always coincides with these graphs. For example, there will be an ideal value for every

engine speed at every engine load. This means that if engine speed is plotted on X axis and engine load on Y axis. We

shall get a graph of engine speed vs engine load. The ECU algorithm shall read that get inputs such as engine speed and

engine load. If the 2 match as per the graph then it is fine, however if say they do not match, the ECU algorithm shall

send signals to actuators to make it match. A modern day ECM can contain thousands of such maps. They are also 3D

maps and surface maps.

Lookup tables

A lookup table is a way in which a dependable variable is ‘written’ in conjunction to an independent variable in the

engine management. These variables are obtained from sensors. The values thus obtained are stored in an array which

is termed as lookup tables. The ECU algorithm also uses these values in engine operation

8.1.3) Inputs and Outputs to the ECM

In an ECM, the inputs are from sensors and outputs are to actuators. The sensor ‘senses’ the measured parameter

and in context with it, sends a suitable signal to the ECM. The ECM reads the signal, and runs it in the ECU algorithm ac-

cording to which corrective action to be taken is determined. These corrective actions are then taken by sending corre-

sponding signals to the actuators which actually ‘take action.’

The signals that are exchanged are either of two types,

Analogue: these signals are based on voltage pulses and controlled by Pulse width modulation (PWM). Although useful in itself, it is slowly being overrun by digital signals. The reason is that PWM usually deals with either true (indicated by 1) or false (indicated by 0). Thus it gives an idea of the value of the parameter in question but does not give an extent of the value.

Digital: these signals are based on data of bits each bit with a specific function. This makes it more useful in monitoring and controlling a system. A very simple example of this is the CAN system used (section 7.4)

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8.2) Electronic spark timing

Newer engines typically use electronic ignition systems (ignition controlled by a computer). The computer has a

timing map which is a table with engine speed on one axis and engine load on another axis. Timing advance values are

inserted in this table. The computer will send a signal to the ignition coil at the indicated time in the timing map in order

to spark the spark plug. Most computers from original equipment manufacturers (OEM) are not able to be modified so

changing the timing advance curve is not possible. Overall timing changes are still possible, depending on the engine

design. Aftermarket engine control units allow the tuner to make changes to the timing map. This allows the timing to

be advanced or retarded based on various engine applications.

8.3) Electronic spark control

In its simplest form, electronic ignition retained the conventional distributor with its mechanical spark advance,

merely replacing the points with a non-wearing electronic means of sensing crankshaft position and firing the spark.

Later analogue spark control computers had more sensors to gather information on throttle position, throttle opening

speed, engine speed, manifold vacuum and coolant temperature. The spark advance was set by the computer rather

than by a centrifugal unit in the distributor. Carburetors could be jetted for leaner fuel-air mixtures which burned more

completely with less polluting residue. Today, at the end of the twentieth century, quite ordinary family cars have elec-

tronic engine management systems which have done away with the familiar distributor and carburetor entirely and al-

low previously unheard of performance and fuel economy.

8.4) Idle speed control system

Idle speed control is used by some engine manufacturers to prevent engine stall using engine management. The

goal is to allow engine at as low rpm as possible, yet keep the engine from running rough and stalling when power con-

suming accessories such as air conditioners are turned on.

The control mode selection logic switches to idle speed control when the throttle angle reaches zero.(completely

closed position) position and engine rpm falls below a certain value, and when the vehicle is stationary. Idle speed is

controlled by an electronically controlled throttle bypass valve that allows air to flow around the throttle plate and pro-

duce the same effect as a slightly open throttle would create.

There are various schemes of operating a valve to introduce bypass air for idle control. One relatively common

method is to use a stepper motor to actuate the valve. A stepper motor is a motor which can rotate in either directions.

It rotates in small increments in angular position when pulses are given to it. This makes the stepper motor ideal for the

operation of idle control valve.

Fig – 8.4.1 Idle speed control

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8.5) Air management system

In simple terms, the catalytic converter oxidizes HC and CO to form H2O and CO2. For this it needs oxygen. Air man-

agement system supplies air, directly into the exhaust if the air (and hence the oxygen) in the exhaust is insufficient for

this conversion in the catalytic converter.

We shall discuss the closed loop, dual air management system with dual valve. It is a closed loop as it takes in input

from the oxygen sensor in the exhaust.

It is used in vehicles which have a dual bed converter. It works as follows.

During engine warm up, the divert valve directs air into the switching valve. The switching valve directs the air to

the exhaust manifold.

As the engine reaches closed loop temperature, the ECM commands the switching valve to direct air to the oxidiz-

ing bed. The air pumped into the oxidizing bed has the following effects.

It prevents additional oxygen from flowing across the oxygen sensor, which would give an incorrect reading.

It lowers the temperature of the exhaust manifold. Continued pumping of air into the exhaust manifold after the engine has reached normal operating temperature could produce additional NOx.

It makes the oxidizing bed of the catalytic converter operate at maximum efficiency without interfering with the effi-ciency of the reduction bed which is upstream to the introduced oxygen.

During warmup time and during deceleration the ECM commands the divert valve to dump the air, using the divert

valve as there is no other place to send it. If during these conditions, air were to be continuously introduced into any

part of the exhaust, the converter will quickly overheat. A schematic figure of the air management system is as shown

in Fig 8.4.1.

Fig – 8.5.1 Air management system.

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Chapter 9 – Sensors And Actuators


9 – Sensors and Actuators

SENSORS: Thermisters, inductive sensors, position sensors (rotary and linear), Pressure sensors, Knock sensors, Hot wire and

thin film air flow sensors, vortex flow/turbine fluid flow sensors, optical sensors, oxygen sensors, light sensors, methanol sensor,

rain sensor, operating principles, application and new developments in the sensor technology.

ACTUATORS: Introduction, function, operating principles, construction of solenoid actuators, relays, motorizes actuators, thermal

actuators, electrohydraulic actuators, electromechanical valve actuators etc. application and new developments in actuator

technology

9.1) SENSORS PRINCIPLES

Sensors are those systems/components that give an electrical signal that is relative to the parameter they are

measuring. These are extensions of transducers. All sensor use transducer technology, in conjunction with other sys-

tems/technology to measure the given parameter and give a suitable output

9.1.1) Thermisters

A thermistor is a type of resistor with resistance varying according to its temperature. The word is a combination of

thermal and resistor. Thermisters are of 2 types, they are given as follows

NTC Type

To measure the temperature of air and fluid in vehicle sensor materials which change their electrical resistance

with effect of heat is used. Most of these sensors are NTC Resistors, for example the coolant temperature sensor, the

changed air temperature sensor. Consider the coolant temperature sensor. The sensor consists of a semi conductor

material which has the negative temperature co-efficient. This means the resistance of sensor drops as temperature in-

creases. NTC Resistors are therefore also known as negative temperature co-efficient thermisters. The drop is resistors

as temperature increases is caused by the increased reaching of electrons from the atomic bombs. The higher the tem-

perature, the more free electrons there are available for electrical flow. This increases the conductivity of the material.

The drop in resistor is registered by the control module and converted into corresponding temperature value.

Fig – 9.1.1.1 – NTC type sensor behaviour

PTC Type

NTC Resistors cannot be used for vary high temperature because the semi conductors will be destroy in the pro-

cess. Instead PTC resistors, the positive temperature co-efficient are used. As in the case of measuring emission tem-

perature PTC resistors consists of special metal alloy whose resistance increases with temperature. They therefore are

also known as positive temperature co-efficient thermistors.

The increase in resistance is caused by the increase in thermal oscillation of the atoms as temperature rises. These

thermal oscillation impede the flow of electrons. In other words the resistance increases. The increase in resistance is

registered by the control volume and converted into corresponding temperature value.

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Chapter 9 – Sensors and Actuators


Fig – 9.1.1.2 PTC Type sensor

9.1.2) Inductive sensors

Inductive sensors are based on the principle of electromagnetic induction. In this usually there is a moving magnet

and a stationary coil. The change in the flux cutting the coil generates an emf in the coil which is then measured. It gives

a relative position and velocity of the magnet. Inductive sensors such as wheel speed sensors and crank shaft position

sensors are extensively used in a vehicle.

The Crank shaft position sensor, for example consists of a permanent magnet, a soft iron core and a stationery coil.

The sensor is located on the engine housing and is separated from the fly wheel by an air gap. The fly wheel may have

teeth or grooves. As the flywheel rotates, it hinders the flux which is interacting with the coil. This generates and emf

which is sensed by the ECM.

9.1.3) Resistive sensors

These are based on resistance change of a conductor. It is called a potentiometer. Its principle of operation is that

the resistance of any conductor is directly proportional to its length and inversely proportional to the cross sectional ar-

ea. A sliding jockey is connected to a coiled resistor, one end of the coil is connected to a voltage supply and the other

end is connected to the jockey. As V=IR, Changing resistance causes a linear change in voltage which is measured.

Fig – 9.1.3.1 Principle of resistive sensors

9.1.4) Optical sensors

Optical sensors are based on photodiodes. A photodiode is a type of photodetector capable of converting light into

either current or voltage, depending upon the mode of operation.

Photodiodes are similar to regular semiconductor diodes except that they may be either exposed (to detect vacu-

um UV or X-rays) or packaged with a window or optical fiber connection to allow light to reach the sensitive part of the

device. In this sense, there is a toothed member, which alternatively exposes and opposes the light beam from hitting

the photo diode. This causes a pulse to be generated, the frequency of which is the same as the frequency of obstruc-

tion

Fig – 9.1.4.1 Principle of Optical sensor

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9.1.5) Piezoelectric transducer

Piezoelectricity is the ability of some materials (notably crystals and certain ceramics) to generate an electric po-

tential in response to applied mechanical stress. This means that when force is applied on these materials, it induces a

voltage that can be measured

Fig – 9.1.5.1 piezoelectric phenomenon

9.2) Automotive sensors explanation

It seemed most feasible to list the sensors in tabular form. Figures for all the sensors are given in the figure gallery.

Section 9.2.1. in the table below, in ‘Principle’ coloumn, the bolded name is the one that is described.

Sr

.

Name Principle Position Description

1 Manifold

Absolute

pressure

(MAP)

sensor

Mechanical

Piezoelectric,

Capacitive.

In intake

manifold

A manifold absolute pressure sensor (MAP) is one of

the sensors used in an internal combustion engine's

electronic control system. Engines that use a MAP

sensor are typically fuel injected. The manifold abso-

lute pressure sensor provides instantaneous mani-

fold pressure information to the engine's electronic

control unit (ECU). This is necessary to calculate air

density and determine the engine's air mass flow

rate, which in turn is used to calculate the appropri-

ate fuel flow.

2 Knock

sensor

Piezoelectric Near com-

bustion

chamber

Sound consist of pressure covers which for example

dissipates through the air through solid materials

such as metal. Acoustic sensors are used for measur-

ing pressure waves one such example are knock Sen-

sors which registers combustion noise in the engine.

Knock sensor is bolted to the crank case. The actual

sensor element is a ring shape piezzo ceramic.

The sound osscilation are transferred by the

crank case initially to the seismic mass. This seismic

mass transfers to oscilation to the piezzo element in

the form of pressure forces. These forces trigger

electrical alterations voltage signaling in the piezzo

element. They picked of by contact plates and pro-

cessed further in the control module.

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3 Hot wire

thin film

air flow

sensor

thermister Intake

manifold

It is usually located between the air cleaner and the

throttle valve. The sensor element consists of the

ceramic chip on which different resistors are located.

One of these is an electrically heated platinum resis-

tor. The proportion of the intake is lead passed

these resistors and cools it. Immediately next to is a

temperature dependent sensor resistor which regis-

ters the temperature of the heating resistor. Sensors

electronic regulate the temperature at the heating

resistor by varying the voltage. If the air mass flow

changes the amount of heat transferred by heating

resistor to the air flowing pass it also changes. The

electronics detect the change in temperature and

reduce the voltage of the heating resistor until the

set temperature is reached. his controlled voltage

used by engine control module is a measure for the

intake air mass.

4 Crankshaft

position

sensor

Optical, in-

ductive,

Near fly-

wheel

The Crank shaft position sensors consist of a perma-

nent magnet. The soft iron core and a stationery

coil. The sensor is located on the engine housing and

is separated from the fly wheel by an air gap. The fly

wheel may have teeth or grooves.

5 Oxygen

sensors

---------------- Before and

after cata-

lytic con-

verter

The sensor element is a ceramic cylinder plated in-

side and out with porous platinum electrodes; the

whole assembly is protected by a metal gauze. It op-

erates by measuring the difference in oxygen be-

tween the exhaust gas and the external air, and gen-

erates a voltage or changes its resistance depending

on the difference between the two. The sensors only

work effectively when heated to approximately

800°C.

The catalyst used is zirconium oxide

6 Throttle

position

sensor

(TPS)

resistive At throttle

valve but-

terfly

The throttle butterfly is directly connected to the

jockey of the potentiometer type sensor. There is a

coiled resistor placed in a radial manner. The posi-

tion of the throttle butterfly is given by the re-

sistance of the system (and hence the voltage drop

across it)

7 Rain sen-

sors

optical Just below

the wind-

shield

A rain sensor or rain switch is a switching device ac-

tuated by rainfall. The most common rain sensor im-

plementation is based on the principle of total inter-

nal reflection: an infrared light is beamed at a 45-

degree angle into the windshield from the inside of

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the car, near the lower edge as soon as rain falls,

there is an extra layer of water with different refrac-

tive index. This causes some of the incident light to

escape, less light makes it back to the sensor, and

the wipers turn on.

8 Light sen-

sors

Optical Automatic

climate

control

In modern vehicles light intensity is measured for a

whole series of open and closed loop control pro-

cess. Luminious intensity is registered with light sen-

sitive resistors i.e. photo diodes, photo transistors,

and photo elements. Where light sensors are used,

automatic head light mode and Consider measuring

principle of photo diodes using a sunlight sensor for

a lorry. A photo diodes consist of different conductor

layers to which a rev. voltage is applied. This rev.

voltage has the effect of laying only a small amount

of current of flow through this diode. However as

soon as the light falls on the semi conductor materi-

al, electrons are released. The current increases con-

siderably as luninious intensity increases. From

these values control module for automatic air condi-

tioners can determine the extent to which the driv-

ers cabin is being heated up by sun light

9.2.1) Picture gallery

Fig – 9.2.1.1 MAP sensor

Fig – 9.2.1.2 Knock sensor

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Fig – 9.2.1.3 Hot wire thin film MAF sensor

Fig – 9.2.1.4 Crankshaft position sensor

Fig – 9.2.1.5 Oxygen sensor and its voltage curve

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Fig – 9.2.1.6 Throttle position sensor

Fig – 9.2.1.7 Rain sensor

9.3) Actuators

An actuator is a mechanical device for moving or controlling a mechanism or system. In automobiles, actuators are

used for many purposes. The actuators in modern automobiles work when a signal is received from the ECM. This signal

is interpreted and the actuator takes the necessary action. Actuators are also based on hydraulic principles. It is not

necessary that all actuators respond to electric signal only. However, as the ECM is the device which controls almost

everything in a vehicle, it is the electric signal which becomes inevitable. Further on from here, we shall see the basic

principles of some of the actuators used in vehicles.

9.3.1) Solenoid Actuators

A typical electric solenoid actuator is shown in Figure 9.3.1.1. It consists of a coil, armature, spring, and stem.

The coil is connected to an external current supply. The spring rests on the armature to force it downward. The

armature moves vertically inside the coil and transmits its motion through the stem to the valve. When current flows

through the coil, a magnetic field forms around the coil. The magnetic field attracts the armature toward the center of

the coil. As the armature moves upward, the spring collapses and the valve opens. When the circuit is opened and cur-

rent stops flowing to the coil, the magnetic field collapses. This allows the spring to expand and shut the valve.

A major advantage of solenoid actuators is their quick operation. Also, they are much easier to install than pneu-

matic or hydraulic actuators. However, solenoid actuators have two disadvantages. First, they have only two positions:

fully open and fully closed. Second, they don’t produce much force, so they usually only operate relatively small valves.

Fig – 9.3.1.1 Solenoid actuator

9.3.2) Relays

A relay is an electrical switch that opens and closes under the control of another electrical circuit. It works on the

principle of electromagnetic induction. In the original form, the switch is operated by an electromagnet to open or close

one or many sets of contacts

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When a current flows through the coil, the resulting magnetic field attracts an armature that is mechanically linked

to a moving contact. The movement either makes or breaks a connection with a fixed contact. When the current to the

coil is switched off, the armature is returned by a force approximately half as strong as the magnetic force to its relaxed

position. Usually this is a spring, but gravity is also used commonly in industrial motor starters. Most relays are manu-

factured to operate quickly. In a low voltage application, this is to reduce noise. In a high voltage or high current appli-

cation, this is to reduce arcing.

If the coil is energized with DC, a diode is frequently installed across the coil, to dissipate the energy from the col-

lapsing magnetic field at deactivation, which would otherwise generate a spike of voltage and might cause damage to

circuit components. Some automotive relays already include that diode inside the relay case.

9.3.3) Motorized actuators

These are linear travel actuators which control a linear parameter. This is usually based on a simple DC motor,

which has a stationary magnet and a moving coil. These actuators can be made to be precise and accurate with a lease

count in micrometers. As mentioned above, most of them are based on electric DC motor. However, high precision

ones (which are generally not used in cars) use piezoelectric effect to have a travel of a few microns on application of a

high voltage.

The actuator is based on a screw of very fine pitch, which is splined internally and connected to a splined armature

shaft. Rotation of armature causes screw action which actuates the control arm.

9.3.4) Thermal Actuators

Thermal microactuators are commonly either of the "bimetallic" type, or rely on the expansion of a liquid or gas.

Two metals of different coefficient of thermal expansion are used for the purpose. The 2 are fused to gather such

that there can be no relative motion between the fusing surfaces. When the element is heated, the metal with higher

coefficient of linear expansion expands more than the other. This causes the strip to bend. The strip, as it is made of

metals, can be used to conduct electricity. A screw can be adjusted to adjust the position of the contact w.r.t. to the

bimetallic strip.

Whilst thermally actuated devices can develop relatively large forces, the heating elements consume quite large

amounts of power. Also, the heated material has to cool down to return the actuator to its original position; so the heat

has to be dissipated into the surrounding structure. This will take a finite amount of time, and may affect the speed at

which such actuators can be operated.

Fig – 9.3.4.1 Bimetallic strip

9.3.5) Electrohydraulic actuators

Electrohydraulic valve actuators and hydraulic valve actuators convert fluid pressure into motion in response to a

signal. They use an outside power source and receive signals that are measured in amperes, volts, or pressure. Some

electrohydraulic valve actuators and hydraulic valve actuators move rotary motion valves such as ball, plug, and butter-

fly valves through a quarter-turn or more from open to close. Other valve actuators move linear valves such as gate,

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globe, diaphragm, and pinch valves by sliding a stem that controls the closure element. Throttling valves can be moved

to any position, including fully open or fully closed, within the stroke of the valve. Typically, valve actuators are added

to throttling valves as part of a control loop that includes a sensing device and circuitry.

Electrohydraulic valve actuators and hydraulic valve actuators use several different types of actuators. Diaphragm

actuators are used mainly with linear motion valves, but are suitable for rotary motion valves with a linear-to-rotary

motion linkage. Rack-and-pinion actuators transfer the linear motion of a piston cylinder actuator to rotary motion.

They are ideal for automating manually-operated valves. Scotch yoke actuators also transfer linear motion to rotary

motion. With lever and link actuators, a splined or slotted lever attaches to the valve shaft in order to transfer the linear

motion of a diaphragm or piston cylinder to rotary motion. Vane actuators are used only with rotary motion valves.

9.3.6) Electro mechanic actuators

All actuators discussed above can be considered as electromechanical actuators. These are devices that convert

electric signal into mechanical motion. All the actuators discussed above are of such type.

9.4) Some Automotive Actuators Throttle control valve

EGR valve

Air pump in air management system

Automatic door locks

Heated seat element cutoff actuator

Remote trunk opener

Motors used in opening rooftop of convertibles

TCS/ABS hydraulic braking/pressure release devices

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Chapter 10 – Lighting


10 – Lighting

Types of lamps ,energy demands of lamps,. Head lamps: construction and types, setting and control. Reflectors:

parabolic, homifocal, poly-elipsoidal. Fog lamp, side lamp, tail lamp, parking lamp, brake warning lamp, , traffica-

tors, blinkers, flashers, electronic flasher circuit, instrument panel.

10.1) Types of lamps

There are various lamps used in cars. They are as follows

Forward Illumination

Head lamps:

dipped beam: Dipped-beam (also called low, passing, or meeting beam) headlamps provide a light distribution to

give adequate forward and lateral illumination without blinding other road users with excessive glare

Main beam: (also called high, driving, or full beam) headlamps provide an intense, centre-weighted distribution of

light with no particular control of glare.

Auxiliary lamps:

Driving lamps "Driving lamp" is a term deriving from the early days of nighttime driving, when it was relatively rare

to encounter an opposing vehicle. Only on those occasions when opposing drivers passed each other would the dipped

or "passing" beam be used. The full beam was therefore known as the driving beam, and this terminology is still found

in international ECE Regulations, which do not distinguish between a vehicle's primary (mandatory) and auxiliary (op-

tional) upper/driving beam lamps.

Fog lamps: Front fog lamps provide a wide, bar-shaped beam of light with a sharp cutoff at the top, and are gener-

ally aimed and mounted low They may be either white or selective yellow. They are intended for use at low speed to in-

crease the illumination directed towards the road surface and verges in conditions of poor visibility due to rain, fog,

dust or snow.

Cornering lamps: On some models in North America and Japan, white cornering lamps provide extra lateral illumi-

nation in the direction of an intended turn or lane change. These are actuated in conjunction with the turn signals,

though they burn steadily, and they may also be wired to illuminate when the vehicle is shifted into reverse gear

Spot lights: Police cars, emergency vehicles, and those competing in road rallyes are sometimes equipped with an

auxiliary lamp in a swivel-mounted housing attached to one or both a-pillars, directable by a handle protruding through

the pillar into the vehicle.

Conspicuity devices

Retro-reflectors: The most basic vehicle conspicuity devices are retroreflectors (also reflex reflectors or, archaically, cat's eyes - not to be confused with the reflective road markings), which despite emitting no light on their own, are reg-ulated as automotive lighting devices. These devices reflect light from other vehicles' headlamps back towards the light source, that is, other vehicles' drivers. Thus, vehicles are conspicuous even when their electrically-powered lighting sys-tem is deactivated or disabled

Front position lamps (parking lamps): Nighttime standing-vehicle conspicuity to the front is provided by front position lamps, known as parking lamps or parking lights in North America, sidelights in UK English, and in other regions as posi-tion lamps, standing lamps, or city lights.

Rear position lamps-tail lamps (power requirement 5W): Night time vehicle conspicuity to the rear is provided by rear position lamps (North American terms: taillamp, taillight, tail lamp, tail light; UK term rear light). These are required to produce only red light, and to be wired such that they are lit whenever the front position lamps are illuminated—including when the headlamps are on. Rear position lamps may be combined with the vehicles brake lamps, or separate

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from them. In combined-function installations, the lamps produce brighter red light for the brake lamp function, and dimmer red light for the rear position lamp function.

Rear registration plate lamp: The rear registration plate must be illuminated by a white lamp whenever the position lamps are active. The light may however not be directed to the rear.

Daytime running lamps: Some countries permit or require vehicles to be equipped with daytime running lamps (DRL). These may be functionally-dedicated lamps, or the function may be provided by e.g. the low beam or high beam head-lamps, the front turn signals, or the front fog lamps, depending on local regulations

Rear fog lamps (power requirement 21W): In Europe and other countries adhering to ECE Regulation 48, vehicles must be equipped with one or two bright red "rear fog lamps" (or "fog tail lamps"), which are switched on manually by the driver in conditions of poor visibility to enhance vehicle conspicuity from the rear

Emergency vehicle lights: Emergency vehicles such as fire engines, ambulances, police cars, snow-removal vehicles and tow trucks are usually equipped with intense warning lights of particular colours. These may be motorised rotating bea-cons, xenon strobes, or arrays of LEDs.

Taxi displays: Taxicabs are distinguished by special lights according to local regulations. They may have an illuminated "Taxi" sign, a light to signal that they are ready to take passengers, and an emergency panic light the driver can activate in the event of a robbery to alert passersby to call the police.

Signaling Devices

Turn signals (power requirement 7W): Turn signals (properly directional indicators or directional signals, also "indica-tors," "directionals," "blinkers," or "flashers") are signal lights mounted near the left and right front and rear corners, and sometimes on the sides of vehicles, used to indicate to other drivers that the operator intends a lateral change of position (turn or lanechange).

Hazard lights: International regulations have since the 1960s required vehicles to be equipped with a control which, when activated, flashes the left and right directional signals, front and rear, all at the same time and in phase. This func-tion is meant to be used to indicate a hazard such as a vehicle stopped in or alongside moving traffic, a disabled vehicle, an exceptionally slow-moving vehicle, or a vehicle participating in a funeral procession.

Brake lights (power requirement 15W to 36W): Red steady-burning rear lights, brighter than the taillamps, are activat-ed when the driver applies the vehicle's brakes. These are called brake lights or stop lamps. They are required to be fit-ted in multiples of two, symmetrically at the left and right edges of the rear of every vehicle.

Reversing light(power requirement 24W): To provide illumination to the rear when backing up, and to warn adjacent vehicle operators and pedestrians of a vehicle's rearward motion, each vehicle must be equipped with at least one rear-mounted, rear-facing reversing lamp (or "backup light")

Ornamental lights

10.2) Head lamps

10.2.1) Halogen bulb

A halogen lamp is an incandescent lamp where a tungsten filament is sealed into a compact transparent envelope

filled with an inert gas, plus a small amount of halogen such as iodine or bromine. The halogen cycle prevents darkening

of the bulb. The halogen lamp can operate its filament at a higher temperature than in a standard gas filled lamp of sim-

ilar wattage without loss of operating life. This gives it a higher efficacy (10-30%). It also gives light of a higher color

temperature compared to a non-halogen incandescent lamp. Alternatively, it may be designed to have perhaps twice

the life with the same or slightly higher efficacy.

The reason that these bulbs don’t blacken is that in older gas bulbs, over a period of time, about 10% of filament

metal evaporates and gets deposited on the glass wall. The halogen in the halogen bulb prevents that. When tungsten

filament metal evaporates, it forms tungsten halide; this is not deposited on the wall due to temperature. The convec-

tion current causes this tungsten halide to move back to the filament at some point or the other and tungsten is again

deposited on the filament.

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Fig – 10.2.1.1 Halogen bulb, twin filament

10.2.2) Headlight reflectors

The light produced by the bulb is insufficient as it is directed toward a particular direction only. To give the light

emitted from the bulb, a definite pattern to cover considerate amount of longitudinal and lateral visibility. Headlights

are used which reflect the light from the bulb into a particular pattern on the road.

The object of the headlight reflector is to direct the random rays of light produced by the source (i.e. the bulb) into

a concentrated beam of light by applying laws of reflection. Bulb position relative to the reflector is important. It de-

termines the exact pattern of the light beam. Slight deviations in bulb position w.r.t. reflector can cause magnified dis-

tortions in headlight pattern.

Fig – 10.2.2.1 focal point

A reflector is basically a layer of silver, chrome or aluminum deposited on a smooth polished surface such as brass

or glass. As shown in the figure above, the reflectors used in automobile headlamps are all concave reflectors

PARABOLIC REFLECTOR

A parabolic reflector is one in which if the source of light is kept at the focal point, all the light rays will end up par-

allel to the principle axis. The light intensity is maximum at the centre, except from the light cut off by the bulb itself.

The intensity diminishes as one moves away from the centre. The parabolic reflector is as shown in fig 10.2.2.1

BIFOCAL REFLECTOR

The bifocal reflector, as the name suggests has 2 different curved surfaces with 2 focal points. This helps to take

the advantage of light striking the lower reflector area. The parabolic section of the down section is designed to reflect

the light further down to improve near the car visibility. This system is not suitable with twin filaments bulbs and is only

used for vehicles with 4 head lamps (Mercedes E class, Jaguar S type).

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Fig – 10.2.2.2 Bifocal lens

HOMIFOCAL REFLECTOR

A homifocal reflector is made up of a number of sections, each with a common focal point, this allows shorter focal

length and hence overall depth of the light unit decreases. The effective luminous flux is also increased. It can be used

with a twin filament bulb to give a dip and main beam. The light from the main reflector gives normal long range light-

ing, and the auxiliary reflectors improve near field and lateral visibility.

Fig – 10.2.2.2 Homifocal reflector

POLYELIPSOIDAL HEADLIGHT SYSTEM

It was introduced by Bosch in 1983. It allows the light produced to be as good, or in some cases even better than

conventional lights, but with a light opening area of less than 30cm2. This is achieved by using a CAD designed elliptical

reflector. A shield Is used to ensure particular pattern. This can be a clearly defined cutoff lines or even intentional blur-

riness in the image. These can be only used with single filament bulbs and are found in four headlamp vehicles.

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Fig – 10.2.2.3 Poly Ellipsoidal headlight system

10.2.3) Headlight lenses

A good headlight should have a powerful and far reaching central beam, around which the light is distributed both

horizontally and vertically in order to illuminate as much an area of the road surface as possible. The beam formation

can be considerably improved by passing the reflected light through a transparent block of lenses. It is the function of

the lenses to partially redistribute the reflected light beam and any stray rays so that overall road illumination is im-

proved with minimum glare.

Lenses work on the principle of refraction. The headlamp front glass is made up of a large number of small rectan-

gular zones, each zone being formed optically in the shape of a concave flute or a combination of flutes and prisms. The

shape of these sections is such that when a roughly parallel beam of light passes through the glass, each individual ele-

ment is redirected to obtain better beam design.

The flutes control the horizontal distribution of light. At the same time, they sharply bend the rays downward, to

give diffused local lighting just near the vehicle. Many headlights are now made with clear lenses. This means that all

the reflection is being done by the reflector only (e.g. BMW series 5, series 7).

10.3) Electronic flasher circuit

10.3.1) Introduction

Direction indicators have a number of requirements which are governed by legislature. They are as follows.

1. Light must be amber in colour.

2. Flashing must be in phase.

3. Flashing rate must be between 1-2 per second.

4. On a fault in the circuit, there should be an indication in the instrument panel.

5. If one bulb fails, others need to continue flashing.

6. An audible noise of ‘tick-tock’ nature is necessary to indicate the flashing of the lights.

10.3.2) Flasher Unit

A schematic circuit diagram of an electronic flasher unit is as shown in Fig 10.3.2.1. The operation of this unit is

based around an integrated circuit (IC). The type shown can operate at least four 21W bulbs (front and rear) and two

5W bulbs (sides) for several hours if required in hazard mode. Flasher units are rated by the number of bulbs they are

capable of operating. When towing a trailer or caravan, it must be able to operate the bulbs on the trailer/caravan also.

Most units use a relay for the actual switching as this is not susceptible to voltage spikes and also provides the audible

signal.

The electronic circuit is constructed together with the relay, on a printed circuit board. Very few components are

used as the IC is specially designed for the purpose.

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The IC itself has 3 main sections, the relay driver, an oscillator and a bulb failure circuit. A zener diode is built in the

oscillator section to ensure constant voltage such that the frequency of operation will remain constant in the range of

10-15V. The timer for the oscillator is controlled by an R1 and C. The values are often set to give an ON/OFF ratio of 1:1

and a frequency of 1.5Hz. the ON-OFF signal produced by the oscillator is passed to the driver circuit, which is a Darling-

ton pair with a diode connected to prevent damage due to generation of back emf, when relay turns ON and OFF.

Bulb failure is recognized when the volt drop across the low value resistor R2 falls. The bulb failure circuit causes

the oscillator to double the speed of operation. Extra capacitors can be used to protect the circuit against transient

voltages and for interference problems. Fig – 10.3.2.2 shows the actual ‘packaging’ of the flasher unit.

Fig – 10.3.2.1 Electronic flasher circuit

Fig – 10.3.2.2 Electronic flasher unit packaging

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Chapter 11 – Accessories


11 – Accessories

Accessories: Instrument panel, Electric horn, wipers, fuel pump, power operated windows etc.

11.1) Function of Instrument panel

Vehicle conditioning monitoring (VCM) is a technique when relevant vehicle performance parameters are dis-

played to the driver. The purpose of this is to either just to keep the driver informed with any warnings in response to

which the driver may take action. VCM covers the following:

High engine temperature

Low fuel

Low brake fluid

Worn out brake pads

Low coolant level

Low screen washer fluid

Low outside temperature

Bulb failure

Doors, bonnet open warning

These are the warnings for which the driver must be alerted so as to avoid catastrophic outcomes. There are other

parameters also which are displayed ‘all the time’ when the car is running, they are

Engine speed

Engine rpm

Indicator for blinker

Indicator for headlight

Engine rpm

Fuel level

Engine temperature

Odometer

The number of information that is given to the driver is limited, owing to the safety aspects. If too much infor-

mation is given to the driver, his mind may get diverted and can inhibit a residual danger.

Another system used is a trip computer. The trip computer is an evolved version of the trip meter. The trip meter

used to turn mechanically and give us the distance covered in kilometer or miles, whatever the convention used. It is

different from the odometer that the trip meter can be set to zero, before starting of a ‘trip.’

The trip computer correlates the distance, time, speed and fuel economy. It aims to give precise information as to

how much can the car run on the amount of fuel that it has in the fuel tank etc. its functions are given more elaborately

below:

Time and date

Elapsed time, or a stop watch

Estimated time of arrival

Average fuel consumption

Range on remaining fuel

Trip distance

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11.2) Visual displays

Although the analogue system has almost become obsolete in other applications, we find that in vehicles, even

digital displays are represented in an analogue manner. This is because, analogue displays reduce driver processing

time, leaving more time to interpret the actual driving conditions.

For example, an analogue engine temperature gauge, with its needle in the middle (not on H or C, but in the mid-

dle) is easy to read and interpret. The driver can easily see that the value is within limits. The same display, however if

showed 70oC, it would be difficult to interpret.

Over the years, there has been considerate amount of advancement in display technologies of automobiles. There

are those that are still used such as analogue ones, and the digital ones have also been evolving. Some of the most

commonly used display techniques is given below

11.2.1) Light emitting diode displays

A light-emitting diode, usually called an LED is a semiconductor diode that emits incoherent narrow-spectrum light

when electrically biased in the forward direction of the p-n junction, as in the common LED circuit. This effect is a form

of electroluminescence.

In automobile instrumentations, it is widely used for showing speed, to odometer, to fuel level and other things.

The number is represented by the ‘8’ Fashion, and other things are shown by bar graphs (See Fig 11.2.1.1).

Fig – 11.2.1.1 LED type instrumentation basic shapes

11.2.2) Liquid crystal displays

LCDs use liquid crystals that do not melt directly, but get transformed to a paracrystalline form in which the mole-

cules are partially ordered. In this stage, the material is a cloudy, translucent fluid, still having optical properties of sol-

ids. There three types of these crystals

1. Smectic: parallel rod shaped molecules, arranged in layers but with no pattern in each layer

2. Nemetic: parallel rod shaped molecules, not arranged in layers

3. Cholestric (twisted nematic): parallel rod shaped molecules, arranged in layers, with each layer having spiral or helical orientation

Mechanical stress, electric and magnetic fields, pressure and temperature can alter molecular structure of liquid

crystals. A liquid crystal also scatters light that shines on it. Because of these properties, liquid crystals are used to dis-

play letters, and numbers in calculators and such devices. Advancement in technology has caused to arrange these in an

array to create a pixel matrix. These can be used to give colour display by the use of three colours on each pixel, viz

RGB.

One type of display incorporating choleristic type is explained here. This display is achieved by only allowing polar-

ized light to enter the crystal. As the light passes through the crystal, it rotates by 90o. The light then passes to a second

polarizer which is at 90o to the first one. Thus reflection takes place and all the light is reflected. However, when a volt-

age of 10V at 50Hz is applied, the crystal orientation changes and it no longer turns the light by 90o. This causes a dark

spot to appear on the screen. These areas are strategically placed on the display panel in the same manner as LEDs are

arranged, to get meaningful designs.

11.2.3) Vacuum fluorescent displays

Unlike liquid crystal displays, a VFD emits a very bright light with clear contrast and can easily support display ele-

ments of various colours.

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The device consists of a hot cathode (filaments), anodes (phosphor) and grids encased in a glass envelope under a

high vacuum condition. The cathode is made up of fine tungsten wires, coated by alkaline earth metal oxides, which

emit electrons when heated by an electric current. These electrons are controlled and diffused by the grids, which are

made up of thin metal. If electrons impinge on the phosphor-coated plates, they fluoresce, emitting light. Unlike the or-

ange-glowing cathodes of traditional vacuum tubes, VFD cathodes are efficient emitters at much cooler temperatures,

and are therefore essentially invisible. Each of these displays are strategically placed on the display panel in the same

manner as LEDs are arranged, to get meaningful designs.

11.3) Fuel level Gauge

The fuel level gauge is usually of resistive type. Other types using electromagnetic induction, variable capacitance

are also in use, however, the variable resistive gauge is by far the most used in today's automobiles.

In Fig 11.3.1, the float is attached to a guide which travels on a rod in the fuel tank. The float is directly attached to

the jockey. According to the fuel level, the float rises/falls and changes the resistance. This change in resistance of the

circuit causes a change in the voltage drop across the circuit, which is measured and fuel level calculated.

Fig – 11.3.1 Schematic representation of a fuel gauge

11.4) Temperature gauge

Temperature gauge are of 2 types. One is incorporating the bimetallic principle (section 9.3.4) and the other is of

the thermister type (section 9.1.1).

11.5) Electric horn

Automobile horns are usually electric klaxons, driven by a flat circular steel diaphragm that has an electromagnet

acting upon it and is attached to a contactor that repeatedly interrupts the current to the electromagnet. This arrange-

ment works like a buzzer or electric bell. There is usually a screw to adjust the distance/tension of the electrical con-

tacts for best operation.

Refer fig 11.5.1, when the horn switch is closed, the relay coil is energized which closes relay switch and current

flows through the horn winding. This magnetizes the core and attracts the tone disc through the connection and dia-

phragm. As soon as that happens, the contact breaks, which de-energizes the winding, magnetic flux falls, and tone disc

is sent back. Again contact is made and again the cycle continues. This happens several times in a second, and causes

the tone disc to vibrate against the diaphragm to produce sound.

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Fig – 11.5.1 Electric horn

11.6) Wipers

A windscreen wiper (windshield wiper in North America) is a device used to wipe rain and dirt from a windscreen.

Almost all automobiles are equipped with windscreen wipers, often by legal requirement.

Wipers can also be fitted to other vehicles, such as buses, trams, locomotives, aircraft and ships.

A wiper generally consists of an arm, pivoting at one end and with a long rubber blade attached to the other. The

blade is swung back and forth over the glass, pushing water from its surface. The speed is normally adjustable, with

several continuous speeds and often one or more "intermittent" settings. Most automobiles use two synchronized radi-

al type arms, while many commercial vehicles use one or more pantograph arms. Mercedes-Benz pioneered a system

called the Monoblade in which a single wiper extends outward to get closer to the top corners, and pulls in at the ends

and middle of the stroke, sweeping out a somewhat 'W'-shaped path.

Wipers may be powered by a variety of means, although most in existence today are powered by an electric motor

through a series of mechanical components, typically two 4-bar linkages in series or parallel. Vehicles with air operated

brakes sometimes use air operated wipers, run by bleeding a small amount of air pressure from the brake system to a

small air operated motor mounted just above the windscreen. These wipers are activated by opening a valve which al-

lows pressurized air to enter the motor.

Most windscreen wipers operate together with a windscreen washer; a pump that supplies water and detergent

(usually a blend called windscreen wiper fluid) from a tank to the windscreen through small nozzles, mounted on the

hood or on the wipers, known as a 'wet-arm' system.

Fig – 11.6.1 Wiper mechanism run by motor using single slider crank mechanism

11.7) Fuel pump

Nowadays, the fuel pump is located inside of the fuel tank and is usually electric. The pump creates positive pres-

sure in the fuel lines, pushing the gasoline to the engine. The higher gasoline pressure raises the boiling point. Placing

the pump in the tank puts the component least likely to handle gasoline vapor well (the pump itself) farthest from the

engine, submersed in cool liquid. Another benefit to placing the pump inside the tank is that it is less likely to start a

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fire. Though electrical components (such as a fuel pump) can spark and ignite fuel vapors, liquid fuel will not explode

due to absence of air, and therefore submerging the pump in the tank is one of the safest places to put it.

The ignition switch does not carry the power to the fuel pump, instead it activates a relay which will handle the

higher current load.

Modern engines utilize solid-state control which allows the fuel pressure to be controlled via pulse-width modula-

tion of the pump voltage.[1] This increases the life of the pump, allows a smaller and lighter device to be used, and re-

duces electrical load and thereby fuel consumption.

Fig – 11.7.1 Electric fuel pump

11.8) Power operated windows

THE LIFTING MECHANISM

The window lift on most cars uses a mechanical linkage to lift the window glass while keeping it level. A small elec-

tric motor is attached to a worm gear and several other spur gears to create a large gear reduction, giving it enough

torque to lift the window.

An important feature of power windows is that they cannot be forced open -- the worm gear in the drive mecha-

nism takes care of this. Many worm gears have a self-locking feature because of the angle of contact between the worm

and the gear. The worm can spin the gear, but the gear cannot spin the worm -- friction between the teeth causes the

gears to bind.

The linkage has a long arm, which attaches to a bar that holds the bottom of the window. The end of the arm can

slide in a groove in the bar as the window rises. On the other end of the bar is a large plate that has gear teeth cut into

it, and the motor turns a gear that engages these teeth.

The same linkage is often used on cars with manual windows, but instead of a motor turning the gear, the crank

handle turns it. In the next section we'll learn about some of the neat features some power windows have, including the

child lockout and automatic-up.

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ELICTRICAL AND WIRING SYSTEM

On this system, the power is fed to the driver's door through a 20-amp circuit breaker. The power comes into the

window-switch control panel on the door and is distributed to a contact in the center of each of the four window

switches. Two contacts, one on either side of the power contact, are connected to the vehicle ground and to the motor.

The power also runs through the lockout switch to a similar window switch on each of the other doors.

When the driver presses one of the switches, one of the two side contacts is disconnected from the ground and

connected to the center power contact, while the other one remains grounded. This provides power to the window mo-

tor. If the switch is pressed the other way, then power runs through the motor in the opposite direction.

Fig – 11.8.1 lifting mechanism of a window

Fig – 11.8.2 Wiring of power windows.

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Chapter 12 – Telematics


12 – Telematics

Introduction, Services and application, telematics system view and present developments in telematics technol-

ogy.

12.1) Introduction

The term telematics is used in a number of ways:

It can be defined as the integrated use of telecommunications and informatics, also known as ICT (Information and Communications Technology). More specifically it is the science of sending, receiving and storing information via tele-communication devices.

More commonly, telematics have been applied specifically to the use of Global Positioning System technology integrat-ed with computers and mobile communications technology in automotive navigation systems.

Most narrowly, the term has evolved to refer to the use of such systems within road vehicles, in which case the term vehicle telematics may be used

Vehicle telematics systems may be used for a number of purposes, including collecting road tolls, managing road

usage (intelligent transportation systems), pricing auto insurance, tracking fleet vehicle locations (fleet telematics), cold

store logistics, recovering stolen vehicles, providing automatic collision notification, location-driven driver information

services — and more particularly, dedicated short range communications DSRC in-vehicle early warning (car accident

prevention) notification alerts.

Vehicle telematics systems are also increasingly being used to provide remote diagnostics; a vehicle's built-in sys-

tem will identify a mechanical or electronic problem, and the telematics package can automatically make this infor-

mation known to the vehicle manufacturer service organization. The telematics monitored system is also capable of no-

tifying any problems to the owner of the vehicle via e-mail. Other forthcoming applications include on-demand naviga-

tion, audio and audio-visual entertainment content.

While there are many potential applications for vehicle telematics, the main advantage for transportation safety

advocates is that it will help reduce and ideally eliminate road injuries and road traffic related deaths worldwide

12.2) Telematics architecture

The architecture of telematics is a very complex data transfer process, much of the same way that internet works,

or mobile phones works. In simple forms, it can be explained by Fig 12.2.1 below.

Fig – 12.2.1 Telematics architecture

What data is to be collected is pre-fed in the ECM algorithm. This data is collected and sent to the modem or sms

device, it must be noted that these 2 devices are integral with the car, but for simplicity sake, these are shown as sepa-

rate blocks outside the vehicle. The data is then sent to a satellite, which reads redirects the data back to the data ac-

quisition system or the user. If there is any action to be taken, it is done and the data is sent back to the car via the

same route. The action taken may not be directed to the same car. For example, in case the car meets an accident, the

‘action’ taken is to alert the authorities such as police and the hospital in that area.

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The data is sent is in coded form, the code includes destination code, the data itself and many other such parame-

ters required for such a system.

12.3) Services and applications

Vehicle tracking

Vehicle tracking is a way of monitoring the location, movements, status and behavior of a vehicle or fleet of vehi-

cles. This is achieved through a combination of a GPS receiver and an electronic device (usually comprising a GSM GPRS

modem or SMS sender) installed in each vehicle, communicating with the user (dispatching, emergency or co-

coordinating unit) and PC- or web-based software.

Trailer tracking

Trailer tracking is the technology of tracking the movements and position of an articulated vehicle's trailer unit,

through the use of a location unit fitted to the trailer and a method of returning the position data via mobile communi-

cation network or geostationary satellite communications, for use through either PC- or web-based software.

Cold store freight logistics

Cold store freight trailers that are used to deliver fresh or frozen foods are increasingly incorporating telematics to

gather time-series data on the temperature inside the cargo container, both to trigger alarms and record an audit trail

for business purposes.

Fleet management

Fleet management is the management of a company's vehicle fleet. Fleet management includes the management

of ships and or motor vehicles such as cars, vans and trucks. Fleet (vehicle) Management can include a range of Fleet

Management functions, such as vehicle financing, vehicle maintenance, vehicle telematics (tracking and diagnostics),

driver management, fuel management and health & safety management.

Satellite navigation

Satellite navigation in the context of vehicle telematics is the technology of using a GPS and electronic mapping

tool to enable the driver of a vehicle to locate a position, then route plan and navigate a journey.

Mobile data and mobile television

Mobile data is use of wireless data communications using radio waves to send and receive real time computer data

to, from and between devices used by field based personnel. These devices can be fitted solely for use while in the ve-

hicle (Fixed Data Terminal) or for use in and out of the vehicle (Mobile Data Terminal). See mobile Internet.

Mobile data can be used to receive TV channels and programs, in a similar way to mobile phones, but using LCD TV

devices.

Wireless vehicle safety communications

It is an electronic sub-system in a car or other vehicle for the purpose of exchanging safety information, about such

things as road hazards and the locations and speeds of vehicles, over short range radio links. This may involve tempo-

rary ad hoc wireless local area networks.

Wireless units will be installed in vehicles and probably also in fixed locations such as near traffic signals and emer-

gency call boxes along the road. Sensors in the cars and at the fixed locations, as well as possible connections to wider

networks, will provide the information, which will be displayed to the drivers in some way.

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Intelligent vehicle technologies

Telematics comprise electronic, electromechanical, and electromagnetic devices — usually silicon micro machined

components operating in conjunction with computer controlled devices and radio transceivers to provide precision re-

peatability functions (such as in robotics artificial intelligence systems) emergency warning validation performance re-

construction.

Intelligent vehicle technologies commonly apply to car safety systems and self-contained autonomous electrome-

chanical sensors generating warnings that can be transmitted within a specified targeted area of interest, say within

100 meters of the emergency warning system for vehicles transceiver. In ground applications, intelligent vehicle tech-

nologies are utilized for safety and commercial communications between vehicles or between a vehicle and a sensor

along the road.

Auto insurance

The basic idea of telematic auto insurance is that a driver's behavior is monitored directly while the person drives

and this information is transmitted to an insurance company. The insurance company then assesses the risk of that

driver having an accident and charges insurance premiums accordingly. A driver who drives long distance at high speed,

for example, will be charged a higher rate than a driver who drives short distances at slower speeds.

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13 – Intelligent vehicle systems

Requirements, working, components and system control of the following systems

Antilock braking system, Active suspension, Traction control, Electric power steering, Global positioning system,

Advanced vehicle navigation, Driver assistance concept, Adaptive cruise control. Introduction to intelligent transport

system

13.1) Antilock Braking System

The reason for the development of anti-lock brakes (ABS) is very simple. Under braking conditions if one or more of

the vehicle wheels locks (begins to skid) then this has a number of consequences:

braking distance increases;

steering control is lost;

tyre wear is abnormal.

The obvious consequence is that an accident is far more likely to occur. The maximum deceleration of a vehicle is

achieved when maximum energy conversion is taking place in the brake system. This is the conversion of kinetic energy

to heat energy at the discs and brake drums.

13.1.1) Requirements

Term Explanation

Fail safe system In the event of the ABS system fail-

ing then conventional brakes must

still operate to their full potential.

In addition a warning must be given

to the driver. This is normally in the

form of a simple warning light

Maneuverability

must be main-

tained

Good steering and road holding

must continue when the ABS sys-

tem is operating. This is arguably

the key issue as being able to

swerve round a hazard whilst still

braking hard is often the best

course of action

Immediate re-

sponse

Even over a short distance the sys-

tem must react such as to make use

of the best grip on the road.The re-

sponse must be appropriate

whether the driver applies the

brakes gently or slams them on

hard

Operational

influences

Normal driving and manoeuvring

should produce no reaction on the

brake pedal. The stability and steer-

ing must be retained under all road

conditions. The system must also

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Chapter 13 Intelligent Vehicle Systems


adapt to braking hysteresis when

the brakes are applied, released

and then reapplied. Even if the

wheels on one side are on dry tar-

mac and the other side on ice, the

yaw (rotation about the vertical axis

of the vehicle) of the vehicle must

be kept to a minimum and only in-

crease slowly to allow the driver to

compensate

Controling of

wheels

In its basic form at least one wheel

on each side of the vehicle should

be controlled on a separate circuit.

It is now general for all four wheels

to be controlled on passenger vehi-

cles

Speed range The system must operate under all

speed conditions down to walking

pace. At this very slow speed even

when the wheels lock the vehicle

will come to rest very quickly. If the

wheels did not lock then in theory

the vehicle would never stop!

Other operating

conditions

The system must be able to recog-

nize aquaplaning and react accord-

ingly. It must also still operate on

an uneven road surface. The one

area still not perfected is braking

from slow speed on snow. The ABS

will actually increase stopping dis-

tance in snow but steering will be

maintained. This is considered to be

a suitable trade off

13.1.2) General system descriptions

As with other systems ABS can be considered as a central control unit with a series of inputs and outputs. An ABS

system is represented by the closed loop system block diagram shown in Figure 13.1.2.1. The most important of the in-

puts are the wheel speed sensors and the main output is some form of brake system pressure control. The task of the

control unit is to compare signals from each wheel sensor to measure the acceleration or deceleration of an individual

wheel. From this data and pre-programmed look up tables, brake pressure to one or more of the wheels can be regu-

lated. Brake pressure can be reduced, held constant or allowed to increase. The maximum pressure is determined by

the driver’s pressure on the brake pedal.

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Fig – 13.1.2.1 ABS system.

13.1.3) ABS components

Wheel speed sensors

Most of these devices are simple inductance sensors and work in conjunction with a toothed wheel. They consist

of a permanent magnet and a soft iron rod around which is wound a coil of wire. As the toothed wheel rotates the

changes in inductance of the magnetic circuit generates a signal; the frequency and voltage of which are proportional to

wheel speed. The frequency is the signal used by the ECU. The coil resistance is in the order of 800 to 1000 Ω. Coaxial

cable is used to prevent interference affecting the signal. Some systems now use ‘Hall effect’ sensors.

ECU

The function of the ECU is to take in information from the wheel sensors and calculate the best course of action for

the hydraulic modulator. The heart of a modern ECU consists of two microprocessors such as the Motorola 68HC11,

which run the same programme independently of each other. This ensures greater security against any fault which

could adversely affect braking performance, because the operation of each processor should be identical. If a fault is

detected, the ABS disconnects itself and operates a warning light. Both processors have nonvolatile memory into which

fault codes can be written for later service and diagnostic access. The ECU also has suitable input signal processing stag-

es and output or driver stages for actuator control. The ECU performs a self-test after the ignition is switched on. A fail-

ure will result in disconnection of the system. The following list forms the self-test procedure:

current supply;

exterior and interior interfaces;

transmission of data;

communication between the two microprocessors;

operation of valves and relays;

operation of fault memory control;

reading and writing functions of the internal memory.

All this takes about 300 mS!

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Hydraulic modulator

The hydraulic modulator as shown in Figure 9 has three operating positions:

pressure buildup brake line open to the pump;

pressure holding brake line closed;

pressure release brake line open to the reservoir.

The valves are controlled by electrical solenoids, which have a low inductance so they react very quickly. The mo-

tor only runs when ABS is activated.

13.2) Active suspension

Active suspension is an automotive technology that controls the vertical movement of the wheels via an onboard

system rather than the movement being determined entirely by the surface on which the car is driving. The system

therefore virtually eliminates body roll and pitch variation in many driving situations including cornering, accelerating,

and braking.

This technology allows car manufacturers to achieve a higher degree of both ride quality and car handling by keep-

ing the tires perpendicular to the road in corners, allowing for much higher levels of grip and control.

13.2.1) Methods

An onboard computer detects body movement from sensors located throughout the vehicle, and, using data calcu-

lated by opportune control techniques, controls the action of the suspension.

Solenoid actuated

Solenoids inside the dampers alter the flow of the hydraulic medium and therefore change the dampening charac-

teristics of the suspension setup. The solenoids are wired to the controlling computer.

Hydraulic actuated

Hydraulically actuated suspensions are controlled with the use of hydraulic servomechanisms. The hydraulic pres-

sure to the servos is supplied by a high pressure radial piston hydraulic pump. Sensors continually monitor body move-

ment and vehicle ride level, constantly supplying the computer with new data.

As the computer receives and processes data, it operates the hydraulic servos, mounted beside each wheel. Al-

most instantly, the servo regulated suspension generates counter forces to body lean, dive, and squat during various

driving maneuvers.

In practice, the system has always incorporated the desirable self-leveling suspension and height adjustable sus-

pension features, with the latter now tied to vehicle speed for improved aerodynamic performance, as the vehicle low-

ers itself at high speed.

The drawbacks of this design (at least today) are high cost, and the added complication/mass of the apparatus

needed for its operation. Thus it is only available on premium luxury cars. In addition, "semi-active" systems continue to

advance with respect to their capabilities, narrowing the gap between them and fully active suspension systems.

Colin Chapman - the inventor and automotive engineer who founded Lotus Cars and the Lotus Formula One racing

team - developed the original concept of computer management of hydraulic suspension in the 1980s, as a means to

improve cornering in race cars. Lotus never developed a road going variant.

Computer Active Technology Suspension (CATS) co-ordinates the best possible balance between ride and handling

by analysing road conditions and making up to 3,000 adjustments every second to the suspension settings via electroni-

cally controlled dampers.

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Electromagnetic recuperative

This type of active suspension uses linear electromagnetic motors attached to each wheel independently allowing

for extremely fast response and allowing for regeneration of power used through utilizing the motors as generators.

This comes close to surmounting the issues with hydraulic systems with their slow response times and high power con-

sumption. It has only recently come to light as a proof of concept model from the Bose company, the founder of which

has been working on exotic suspensions for many years while he worked as an MIT professor. His brainchild was only a

strict set of ideas about the way an ideal suspension should behave until, after many years, he developed a unique algo-

rithm for plotting suspension movements. Although many active suspensions have been proposed, the general consen-

sus is that this approach has the most real world potential.[citation needed]

Magneto rheological damper

Another fairly recently developed method incorporates Magneto rheological dampers. Initially developed by Del-

phi Corporation, these dampers are finding increased usage in domestic and foreign brands, mostly in prestige vehicles.

In this system, the damper fluid contains metallic particles, and, through the onboard computer, the dampers'

compliance characteristics are controlled by an electro-magnet. Essentially, increasing the current flow into the damper

raises the compression/rebound rates, while a decrease softens the effect of the dampers. Thus, instead of modifying

the vertical movement of the wheels, it modifies the damping characteristics of the shock absorber, controlling the be-

havior of the car. This type of system is generally referred to as "semi-active".

13.3) Traction control

The steerability of a vehicle is not only lost then the wheels lock up on braking; the same effect arises if the wheels

spin when driving off under severe acceleration. Electronic traction control has been developed as a supplement to

ABS. This control system prevents the wheels from spinning when moving off or when accelerating sharply while on the

move. In this way, an individual wheel which is spinning is braked in a controlled manner. If both or all of the wheels are

spinning, the drive torque is reduced by means of an engine control function. Traction control has become known as

ASR or TCR.

Traction control is not normally available as an independent system, but in combination with ABS. This is because

many of the components required are the same as for the ABS. Traction control only requires a change in logic control

in the ECU and a few extra control elements such as control of the throttle.

Traction control will intervene to:

maintain stability;

reduction of yawing moment reactions;

provide optimum propulsion at all speeds;

reduce driver workload.

An automatic control system can intervene in many cases more quickly and precisely than the driver of the vehicle.

This allows stability to be maintained at a time when the driver might not have been able to cope with the situation.

13.3.1) System Operation

The description that follows is for a vehicle with an electronic accelerator (drive by wire). A simple sensor deter-

mines the position of the accelerator and, taking into account other variables such as engine temperature and speed for

example, the throttle is set at the optimum position by a servomotor. When accelerating the increase in engine torque

leads to an increase in driving torque at the wheels. To achieve optimum acceleration the maximum possible driving

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torque must be transferred to the road. If driving torque exceeds that which can be transferred then wheel slip will oc-

cur on at least one wheel. The result of this is that the vehicle becomes unstable.

When wheel spin is detected the throttle position and ignition timing are adjusted but the best results are gained

when the brakes are applied to the spinning wheel. This not only prevents the wheel from spinning but acts to provide a

limited slip differential action. This is particularly good when on a road with varying braking force coefficients. When the

brakes are applied a valve in the hydraulic modulator assembly moves over to allow traction control operation. This al-

lows pressure from the pump to be applied to the brakes on the offending wheel. The valves, in the same way as with

ABS, can provide pressure buildup, pressure hold and pressure reduction. This all takes place without the driver touch-

ing the brake pedal. The summary of this is that the braking force must be applied to the slipping wheel so as to equal-

ize the combined braking coefficient for each driving wheel.

13.4) Electric power steering

Electric power steering (EPS or EPAS) is designed to use an electric motor to reduce effort by providing assist to the

driver of a vehicle. Most EPS systems have variable assist, which allows for more assistance as the speed of a vehicle

decreases and less assistance from the system during high-speed situations. This functionality requires a delicate bal-

ance of power and control that has only been available to manufacturers in recent years. The EPS system has replaced

the hydraulic steering system (HPS or HPAS) in many passenger cars recently. Although EPS is so far limited to passen-

ger cars, as a higher voltage electrical system is necessary to operate EPS in larger vehicles.

Unlike HPS systems, EPS systems do not require a hydraulic pump, which is belted into the engine. Rather the EPS

system's electric motor is powered by the vehicle's alternator which is belted into the engine. The efficiency advantage

of an EPS system is derived from the fact that it is activated only when needed. Thus, a vehicle equipped with EPS may

achieve an estimated improvement in fuel economy of 3% compared to the same vehicle with conventional HPS. How-

ever, any fuel economy benefit of EPS over HPS can be negated in situations where a vehicle is not driven on straight-

aways very often, or where a vehicle's wheels are out of alignment.

13.5) Global Positioning System

The Global Positioning System (GPS) is the only fully functional Global Navigation Satellite System (GNSS). Utilizing

a constellation of at least 24 Medium Earth Orbit satellites that transmit precise microwave signals, the system enables

a GPS receiver to determine its location, speed, direction, and time.

A typical GPS receiver calculates its position using the signals from four or more GPS satellites. Four satellites are

needed since the process needs a very accurate local time, more accurate than any normal clock can provide, so the re-

ceiver internally solves for time as well as position. In other words, the receiver uses four measurements to solve for

four variables: x, y, z, and t. These values are then turned into more user-friendly forms, such as latitude/longitude or

location on a map, then displayed to the user.

User segment

The user's GPS receiver is the user segment (US) of the GPS. In general, GPS receivers are composed of an antenna,

tuned to the frequencies transmitted by the satellites, receiver-processors, and a highly-stable clock (often a crystal os-

cillator). They may also include a display for providing location and speed information to the user. A receiver is often

described by its number of channels: this signifies how many satellites it can monitor simultaneously. Originally limited

to four or five, this has progressively increased over the years so that, as of 2007, receivers typically have between 12

and 20 channels.

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GPS and cars

GPS has found wide commercial applications in automobile industries. The maps of all major countries/ cities are

fed in the system. This enables the system to accurately identify any address, anywhere! This helps in navigation. To

reach new destinations, where the way is not known, GPS can be used with utter simplicity. The entire of Europe and

America are covered by GPS and road maps. Moreover, the accuracy of these systems is such that they tell you your lo-

cation with less than 10cms of error. This makes it extremely useful in automotive navigation use.

13.6) Adaptive Cruise Control

Adaptive cruise control (ACC) is a cruise control system in some modern vehicles. The system also goes under the

names of active cruise control (ACC) or intelligent cruise control (ICC). These systems use either a radar or laser setup to

allow the vehicle to slow when approaching another vehicle and accelerate again to the preset speed when traffic al-

lows. ACC technology is widely regarded as a key component of any future generations of smart cars, as a form of artifi-

cial intelligence that may usefully be employed as a driving aid.

Types

Laser-based systems are significantly lower in cost than radar-based systems; however, laser-based ACC systems

do not detect and track vehicles well in adverse weather conditions nor do they track extremely dirty (non-reflective)

vehicles very well. Laser-based sensors must be exposed, the sensor (a fairly-large black box) is typically found in the

lower grill offset to one side of the vehicle.

Some systems also feature forward collision warning or Collision Mitigation Avoidance System, which warns the

driver and/or provides brake support if there is a high risk of a rear-end collision.

Radar-based systems are available on many luxury cars as an option for approx. 1000-3000 USD/euro. Laser-based

systems are available on some near luxury and luxury cars as an option for approx. 400-600 USD/euro. Radar-based

sensors can be hidden behind plastic fascias; however, the fascias typically looks different from a vehicle without the

feature. For example, Mercedes packages the radar behind the upper grill in the center; however, the Mercedes grill on

such applications contains a solid plastic panel in front of the radar with painted slats to simulate the slats on the rest of

the grill.

13.8) Drive by wire

Drive-by-wire, DbW, by-wire, or x-by-wire technology in the automotive industry replaces the traditional mechani-

cal and hydraulic control systems with electronic control systems using electromechanical actuators and human-

machine interfaces such as pedal and steering feel emulators. Hence, the traditional components such as the steering

column, intermediate shafts, pumps, hoses, fluids, belts, coolers and brake boosters and master cylinders are eliminat-

ed from the vehicle.

Examples include electronic throttle control and brake-by-wire.

Advantages

Safety can be improved by providing computer controlled intervention of vehicle controls with systems such as

Electronic Stability Control (ESC), adaptive cruise control and Honda's Lane Keeping Assist System (LKAS).

Ergonomics can be improved by the amount of force and range of movement required by the driver and by greater

flexibility in the location of controls. This flexibility also significantly expands the number of options for the vehicle's de-

sign.

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Parking can be made easier with reduced lock-to-lock steering wheel travel as with BMW's Active Steering System,

or automatic parallel parking which is available in some Toyota Prius models and newer European Volkswagen models.

Although neither of these are strictly Steer-by-Wire (SbW) because they retain mechanical linkages, they show the ca-

pabilities that are possible.

Disadvantages

The cost of DbW systems is often greater than conventional systems. The extra costs stem from greater complexi-

ty, development costs and the redundant elements needed to make the system safe. Failures in the control systems can

result in an unstoppable runaway vehicle - if the throttle, ignition and transmission are all beyond the direct control of

the driver there is no effective way to stop the vehicle in such an event.

Steer by Wire

This is currently used in electric forklifts and stockpickers and some tractors. Its implementation in road vehicles is

limited by concerns over reliability although it has been demonstrated in several concept vehicles such as ThyssenKrupp

Presta Steering's Mercedes-Benz Unimog, General Motors' Hy-wire and Sequel and the Mazda Ryuga. A rear wheel SbW

system by Delphi called Quadrasteer is used on some pickup trucks but has had limited commercial success.

Competitors in the DARPA Grand Challenge, an automated driving competition, relied on 100% DbW systems, in

some cases including a SbW system provided by the manufacturer.

In some concept vehicles, steer by wire completely eliminates the steering wheel, and the vehicle is steered by a

joystick.

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Appendix – I – List of Figures, Graphs and Tables


Appendix – I – List of figures, graphs, tables

Graph – 1.2.2.1 Battery rating relations ........................................................................................................................ 8

Table – 1.2.4.1 Battery voltages at different charges .................................................................................................... 9

Fig – 1.2.6.1 A Hydrometer .......................................................................................................................................... 10

Fig – 1.2.6.2 Heavy Duty discharge tester. .................................................................................................................. 10

Fig – 1.3.1 Simplified Nicad battery. ............................................................................................................................ 11

Fig – 1.5.1 Sodium Sulfur battery ................................................................................................................................ 12

Fig – 1.6.1 Swing Battery ............................................................................................................................................. 13

Fig – 2.2.1.1 PEM Fuel cell ........................................................................................................................................... 15

Fig – 2.3.2.1 Alkaline fuel cell ...................................................................................................................................... 16

Table – 3.4.1 Benefits of 42V technology .................................................................................................................... 20

Fig – 3.6.1 Proposed architecture ................................................................................................................................ 23

Graph – 4.2.1.1 Current demands on alternator by time ............................................................................................ 25

Fig – 4.3.1 Vehicle charging system ............................................................................................................................. 25

Fig – 4.4.1.1 Schematic diagram of the dynamo principle .......................................................................................... 26

Fig – 4.5.1.1 voltage regulator ..................................................................................................................................... 27

Fig – 4.5.2.1 Combined current and voltage regulator ................................................................................................ 28

Fig – 4.5.4.1 Electronic voltage regulator .................................................................................................................... 29

Fig – 4.6.1 Alternator exploded view ........................................................................................................................... 29

Fig – 4.6.2 Alternator principle in conjunction with rectification ................................................................................ 30

Fig – 4.6.2.1 Half wave rectification ............................................................................................................................ 30

Fig – 4.6.2.2 Full wave rectifier .................................................................................................................................... 30

Fig – 4.6.2.3 Alternator circuit employing star connection ......................................................................................... 31

Fig – 5.1.1 electrical system of a car ............................................................................................................................ 32

Graph – 5.2.1 engine rpm vs required torque wrt torques. ........................................................................................ 33

Fig – 5.4.1.1 – Standard Bendix drive .......................................................................................................................... 34

Fig – 5.4.2.1 – Folo thru drive ...................................................................................................................................... 35

Fig – 5.4.3.1 – Compression spring bendix drive ......................................................................................................... 35

Fig – 5.4.5.1 – Pre engaged starter. ............................................................................................................................. 37

Fig – 5.4.6.1 – Dyer drive ............................................................................................................................................. 37

Fig 5.5.1 Starter motor solenoid principle. .................................................................................................................. 38

Fig 5.6.1) A Glow plug (tip on the right) ...................................................................................................................... 38

Fig – 6.1.2.1conventional ignition system ................................................................................................................... 41

Fig – 6.2.1 – CDI system ............................................................................................................................................... 42

Fig – 6.3.1 – Direct Ignition system .............................................................................................................................. 43

Fig – 6.4.1 – Principle of hall effect .............................................................................................................................. 43

Fig – 6.4.2 – Hall effect pulse generator and output wave ......................................................................................... 44

Fig – 6.5.1 – Inductive pulse generator. ...................................................................................................................... 44

Fig – 6.7.1 Constant energy systems ........................................................................................................................... 45

Fig – 6.7.1 Spark plug constructional details ............................................................................................................... 46

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Appendix – I – List of Figures, Graphs and Tables


Table – 7.1.2.1 British standard colour codes ............................................................................................................. 47

Fig – 7.1.2.1 – Different connections used in cars ....................................................................................................... 48

Fig – 7.4.1 CAN system layout ..................................................................................................................................... 50

Fig – 7.4.2 CAN signal format – The entire length of the signal is 44 to 108 bits ................................................ 51

Fig – 8.4.1 Idle speed control ....................................................................................................................................... 54

Fig – 8.5.1 Air management system. ........................................................................................................................... 55

Fig – 9.1.1.1 – NTC type sensor behaviour .................................................................................................................. 56

Fig – 9.1.1.2 PTC Type sensor ...................................................................................................................................... 57

Fig – 9.1.4.1 Principle of Optical sensor....................................................................................................................... 57

Fig – 9.1.5.1 piezoelectric phenomenon ..................................................................................................................... 58

Fig – 9.2.1.1 MAP sensor ............................................................................................................................................. 60

Fig – 9.2.1.2 Knock sensor ........................................................................................................................................... 60

Fig – 9.2.1.3 Hot wire thin film MAF sensor ................................................................................................................ 61

Fig – 9.2.1.4 Crankshaft position sensor ...................................................................................................................... 61

Fig – 9.2.1.5 Oxygen sensor and its voltage curve ....................................................................................................... 61

Fig – 9.2.1.6 Throttle position sensor .......................................................................................................................... 62

Fig – 9.2.1.7 Rain sensor .............................................................................................................................................. 62

Fig – 9.3.1.1 Solenoid actuator .................................................................................................................................... 62

Fig – 9.3.4.1 Bimetallic strip ......................................................................................................................................... 63

Fig – 10.2.1.1 Halogen bulb, twin filament .................................................................................................................. 67

Fig – 10.2.2.1 focal point ............................................................................................................................................. 67

Fig – 10.2.2.2 Bifocal lens ............................................................................................................................................ 68

Fig – 10.2.2.2 Homifocal reflector ............................................................................................................................... 68

Fig – 10.2.2.3 Poly Ellipsoidal headlight system .......................................................................................................... 69

Fig – 10.3.2.1 Electronic flasher circuit ........................................................................................................................ 70

Fig – 10.3.2.2 Electronic flasher unit packaging .......................................................................................................... 70

Fig – 11.2.1.1 LED type instrumentation basic shapes ................................................................................................ 72

Fig – 11.3.1 Schematic representation of a fuel gauge ............................................................................................... 73

Fig – 11.5.1 Electric horn ............................................................................................................................................. 74

Fig – 11.6.1 Wiper mechanism run by motor using single slider crank mechanism ................................................... 74

Fig – 11.7.1 Electric fuel pump .................................................................................................................................... 75

Fig – 11.8.1 lifting mechanism of a window ................................................................................................................ 76

Fig – 11.8.2 Wiring of power windows. ....................................................................................................................... 76

Fig – 12.2.1 Telematics architecture ............................................................................................................................ 77

Fig – 13.1.2.1 ABS system. ........................................................................................................................................... 82

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Appendix – II – Simplified Wiring Circuit of a Car


Appendix – II –Simplified Wiring Circuit of a Car

Above figure gives a basic idea of the wiring in the car and the overview of their connection with the common

ground, and different switches for each.

1. CHARGING CIRCUIT: it consists of the generator (dynamo or alternator), a regulator. The generator is run by a pulley and belt arrangement which directly runs from the engine crankshaft. See Chapter 4 for details.

2. STARTING CIRCUIT: it contains the starter motor which attaches to the pinion on starting the engine via a suitable drive. It rotates the flywheel, hence starting the engine. See Chapter 5 for details.

3. LIGHTING CIRCUIT: Head lamps, Tail lamps, Blinkers, Interior lamps etc are all connected in parallel. It must be noted that they glow in pairs only. 2 head lamps or 2 tail lamps, 2 brake lamps, or 2 blinker lights (on the same side). These are connected in series to one switch, however they themselves are parallel for fail safe design. The horn is also shown in this circuit. See Chapter 10, Chapter 11 for details.

4. IGNITION CIRCUIT: it contains the distributor and the spark plugs. It is only found in SI engines. See chapter 6 for details.

5. ACCESSORIES: all remaining accessories are put in here, in parallel, with a separate switch for each. See chapter 11 for some of the accessories details.

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