mechatronics case study

8/7/2019 Mechatronics Case Study

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Mechatronics in Vehicles

Case Study

Yogeesh Sharma

1282, 7 MAE 2

A2305407096


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An increasing number of automatic and semi-automatic transmission systems use

highly complex processing to generate smooth gear changes whilst optimising both

performance and economy. In addition to giving the driver an element of choice over the

degree of sportiness, some advanced systems claim to learn the driving style of the

user and provide the required responsiveness.

Air Bags

Air bags and other defensive mechanisms such as seat-belt tensioners are increasingly

recognised as essential for mitigating the effects of collisions. Air bag technology has

changed from being an extra item on expensive cars to a standard item on everyday

cars, and the number of such devices per car has increased significantly. Whereas a

single air-bag utilised a simple inertial sensor to trigger its actuation, multiple air-bag

systems use a dedicated controller to coordinate the most appropriate response in a

crash.

Security

The majority of cars are now fitted with an integrated access and security system that

includes remote central locking together with alarm and engine immobilisation in the

event of unauthorised entry. A common facility is keylessentry whereby Bluetooth

technology is used to identify an approaching owner. Increasingly, cars are also being

fitted with hidden GPS-based tracking devices to locate the vehicle in the event of theft.

Comfort, Communications and Entertainment

These are the areas where car users are most aware of the impact of mechatronic

systems. Climate control senses the internal temperature and adjusts heater, air

conditioning and fan levels to maintain desired pre-set conditions. The drivers seat

position is remembered and automatically adjusted to suit a new driver based on data

stored in the car keys. The volume of the radio increases to compensate for increased

road noise as the vehicle accelerates. Telephone calls can be voice activated and the

entertainment system detects incoming phone calls and mutes the music accordingly.


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Driver Aids and Information

The driver is increasingly supported by many advice and guidance systems. Lights and

wipers contain sensors that switch them on and off to suit the weather and road

conditions. Warning and advice are provided on such matters as frost on the road,

coolant level and service interval. Parking sensors provide drivers with an audible

warning to prevent a collision during reversing. A trip computer gives information on fuel

consumption and average speed, and cruise-control monitors vehicle speed and sends

commands to the engine management system to maintain a desired speed under

varying road conditions. GPS navigation systems communicate with satellites and

provide the driver with detailed navigation instructions, congestion, and accident black-

spot warnings. When an air bag is deployed, an automated call can be placed to an

emergency processing centre and a conversation with the driver initiated so that

emergency vehicles can be despatched as appropriate.

The Mechatronic Solution to Engine

Management

The first component to be replaced by mechatronics was the troublesome

contact breaker points. From the 1970s onwards, these were replaced by a non-contact

sensor inside the distributor that consisted of a rotating toothed armature (one tooth for

each cylinder) that induces a signal from an electromagnetic transponder each time a

tooth passes in front of it. This signal was then sent to an electronic ignition control unit

that triggered the firing of the coil and hence the spark. This simple innovation produced

a stronger and more reliable spark and removed the need for the replacement and

maintenance of points. At this stage, the mechanical centrifugal and vacuum advance

systems remained. The real revolution came in the mid-1980s when advances in

electronic fuel injection and microprocessor technology enabled complete control over

both ignition and fuel delivery to be contained within a single Engine Control Unit (ECU).

This allows for a much clearer separation between sensing, processing and actuation in


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vehicle is accelerating, decelerating or cruising; all of which influence ignition timing and

fuel ratio.

The mass air flow sensor (MAF) is contained in the air induction system and provides

information on the mass of air entering the engine which is obviously key to determining

the appropriate amount of fuel to inject. The sensor consists of a heated wire element

that is maintained at constant temperature in the varying air flow. The current required

to maintain this temperature is directly proportional to the mass of air flowing. Earlier

sensors measured volume of flow, but as the density of air reduces with temperature,

additional temperature information was required to calculate the mass of air with

sufficient accuracy.

A water temperature sensorallows the ECU to detect a cold start and hence enrich the

fuel. The normal fuel mixture is then adopted when the temperature reaches a pre-set

value.

Actuators

Ignition coils still provide the high voltage for the spark plugs, but in the absence of a

distributor, modern systems often use individual coils for each plug or pair of plugs. Thetriggering signal comes directly from the ECU. Fuel Injectors add a spray of fuel through

a nozzle to the incoming air flow in order to achieve the appropriate air/fuel mix ratio.

Current practice is to use one injector per cylinder, all of which are fed by a constant-

pressure fuel line. Variation in the amount of fuel added is determined by very precise

control over the time that the injector valve is opened on each induction cycle. The

opening of the valve is affected by a signal from the ECU that powers a solenoid within

the injector. Closure is by means of a return spring and the fuel line pressure.


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Processing

The ECU generally takes the form of a module within the engine compartment. The

module contains:

All the electronics for receiving and conditioning the signals from the sensors;

A powerful processor for interpreting the signals and determining the outputs;

Output circuits and amplifiers for driving the ignition coils and fuel injectors.

In addition, the ECU will contain a fault memory that can be read when the vehicle is

serviced.

Conclusion

Consideration was given to three automotive mechatronic systems. The first two,

electronic ignition and electronic fuel injection, are integrated within the engine

management system. They provide examples of how the superior performance of

mechatronics displaced traditional (and relatively unreliable) electrical and mechanical

systems. This is typical of the mechatronic process. It first supplants traditional

technologies and then offers vastly increased functionality because of the flexibility

afforded by software control.

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