PSZ 19:16 (Pind. 1/07)

UNIVERSITI TEKNOLOGI MALAYSIA

DECLARATION OF THESIS / UNDERGRADUATE PROJECT PAPER AND COPYRIGHT

Author’s full name :

AHMAD FAISHAL BIN AHMAD RAZALI

Date of birth : 24 OCTOBER 1986 Title :

LIFT CONTROL BY USING PROGRAMMABLE

LOGIC CONTROLLER (PLC) FOR STUDENTS KITS

Academic Session : 2008/2009 – 2 I declare that this thesis is classified as : I acknowledged that Universiti Teknologi Malaysia reserves the right as follows :

1. The thesis is the property of Universiti Teknologi Malaysia. 2. The Library of Universiti Teknologi Malaysia has the right to make copies for the purpose

of research only. 3. The Library has the right to make copies of the thesis for academic exchange.

Certified by :

SIGNATURE SIGNATURE OF SUPERVISOR

(NEW IC NO. /PASSPORT NO.) NAME OF SUPERVISOR Date : Date :

NOTES : * If the thesis is CONFIDENTIAL or RESTRICTED, please attach with the letter from the organisation with period and reasons for confidentiality or restriction.

CONFIDENTIAL (Contains confidential information under the Official Secret Act 1972)*

RESTRICTED (Contains restricted information as specified by the organisation where research was done)*

√ OPEN ACCESS I agree that my thesis to be published as online open access (full text)

861024-29-5443 ENCIK SHUKRI BIN ABD MANAF 12 MAY 2009 12 MAY 2009

“I declare that I have read this project report and in my opinion this project report is sufficient in

terms of scope and quality for the award of

Bachelor’s Degree of Electrical Engineering (Instrumentation & Control).”

Signature : ..........................................................

Supervisor : ENCIK SHUKRI BIN ABD MANAF

Date : 12 MAY 2009

 

LIFT CONTROL BY USING PROGRAMMABLE LOGIC CONTROLLER (PLC)

FOR STUDENTS KITS

AHMAD FAISHAL BIN AHMAD RAZALI

Submitted to the Faculty of Electrical Engineering

in partial fulfillment of the requirement for the degree of

Bachelor of Electrical Engineering (Instrumentation & Control)

 

 

 

Faculty of Electrical Engineering

Universiti Teknologi Malaysia

 

APRIL 2009

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“Hereby, I declare that this thesis entitled ‘LIFT CONTROL BY USING PLC FOR STUDENTS KITS’ is the

results of my own research except as cited in the references. The project report has not been accepted

for any degree and is not concurrently submitted in candidature of any other degree.

 

Signature : ................................................

Name : AHMAD FAISHAL BIN AHMAD RAZALI

Date : 12 MAY 2009

 

 

 

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Selawat dan Salam ke atas Rasul Junjungan

NABI MUHAMMAD S.A.W.

Untuk Ayah dan Ibu Tersayang

AHMAD RAZALI BIN YAACOB

&

SITI FATIMAH BINTI YAACOB  

 

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ACKNOWLEDGEMENT

Assalamualaikum, greatfull to Allah because of His permission I can finish my final year

project successfull. Special thanks to my committed supervisor, Encik Shukri Bin Abd Manaf for his

guidance, ideas and help throughout this project progress.

My appreciation also goes to my family who just not give the contribution from their helps, but

also to support me troughout this project progress. Also thanks for their encouragement, caring and

spirit that has be given to me.

Besides, don’t forget for my friends, Amer Hamzah who just not give an idea and helpess for

me but also his support to finish this project. Also for Process Control Assistant, Encik Hazrul for his

help to supply me with the equipment.

Nevertheless, my appreciation to my coursemate who are give me the information that I have to

know and all the people who are involve for this project either directly or indirectly. Thank you so

much..

 

 

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ABSTRACT

Elevator is one of the system which can be controlled by programmable logic controller,PLC.

Elevator was build to help the people to moving from one floor to another without consume a lot of

people energy. Besides, its also are used to move the goods or even the car upward or downward in a

few application. Its system have a few basic operation with a few extra operation to make the system

more reliable, efficient and safe to used. There are two types of elevator depending on its application

and its place installed which is hydraulic and cable lifted elevator. The programmable logic

controller, PLC is the one of the best controller to handling this system operation due to its reliable

system. The signal use in PLC is a digital signal and the in some system, it is a analog signal. So, the

input of PLC will change the type of signal first to the suitable form of signal in PLC. It will

implement some range of analog signal to logic one in digital form and implement the logic zero for

the other range. In order to operate the system, the program that was entring by the user will execute

when the instruction is obey by the system situation and send the signal output to operate some

operation depending on the program installed. Therefore, all the system operation will be controlled

according to the sequence of the program.

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TABLE OF CONTENT

CHAPTER TITLE PAGE

DECLARATION OF THESIS ii

DEDICATION iii

ACKNOWLEDGMENT iv

ABSTRACT v

TABLE OF CONTENT vi

LIST OF TABLES x

LIST OF FIGURES xi

LIST OF SYMBOLS xiv

LIST OF APPENDICES xv

1 INTRODUCTION

1.1. History of Elevator 1

1.2. Elevator 3

1.3. Problems Statement 8

1.4. Objective of the Project 9

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1.5. Scope of Project 10

2 LITERATURE REVIEW

2.1. De-Lorenzo Model 12

2.2. Types of Elevator 14

2.2.1. Hydraulic Elevator 14

2.2.2. Cabled-Lifted Elevator 19

2.3. Balance 22

2.4. Safety 23

2.5. Lift Pulley system 25

2.6. Multiple Pulley 26

2.7. Power Flow Through Typical 27

Elevator

2.8. Elevator Operation State 31

2.9. Elevator Motor Drive 32

2.10. AC vs Dc Drive efficiency 34

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2.11. Programmable Logic Controller, 35

PLC

3 METHODOLOGY

3.1. Introduction 42

3.2. Hardware Implementation 43

3.2.1. Pulley System 44

3.2.2. Sensor 45

3.2.3. Sliding Door 46

3.2.4. DC Geared Motor 47

3.2.5. Relay 51

3.2.6. OMRON PLC 53

3.2.7. Others Component 54

3.3. Softwae Implementation

3.3.1. State Diagram 56

3.3.2. Ladder Diagram 58

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4 RESULT AND DISCUSSION

4.1. Introduction 59

4.2. Result 60

4.2.1. Hardware Result 60

4.2.2. Programming Result 63

4.2.2.1. Up and Down operation 63

4.2.2.2. Open and Close door 72

4.3 Discussion 76

5. CONC LUSION

5.1. Conclusion 78

5.2. Problems 79

5.3. Recommendation 80

REFERENCE

APPENDICE A

APPENDICE

x  

LIST OF TABLE

TABLE TITLE PAGE

Table 3.2(a) DC Geared Motor SPG 50 specification 48

Table 3.2(b) DC Geared Motor SPG 20 specifcation 50

 

 

 

 

 

 

 

 

 

 

 

 

 

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LIST OF FIGURE

 

 

 

  FIGURE TITLE PAGE

 

  1.2(a) Elevator 4

2.2(a) Hydraulic Rams 16

2.2(b) Two Hydraulic Rams 17

2.3(a) Empty Car 23

  2.3(b) Occupied Car 23

2.4(a) Centrifugal Governor 24

2.6(a) Multiple Pulley 27

2.7(a) Force on Pulley 29

2.7(b) Pulley system implementation 30

2.11(a) PLC Design 36

2.11(b) Ladder diagram input symbols 38

2.11(c) Ladder diagram output symbols 39

2.11(d) Sequental function chart 40

3.1(a) PLC process diagram 43

3.2(a) Pulley system 44

3.2(b) Double side pulley 45

3.2(c) Limit switch 45

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3.2(d) Level sensor implementation 46

3.2(e) Sliding door implementation 47

3.2(f) DC Geared Motor SPG 50 48

3.2(g) Motor Up/Down implementation 49

3.2(h) DC Geared Motor SPG 20 49

3.2(i) Open/Close door motor implementation 50

3.2(j) Relay 51

3.2(k) Relay circuit 52

3.2(l) OMRON PLC 53

3.2(m) Counterweight 54

3.3(a) CX-Programmer software 55

3.3(b) CX Progrmmer ladder diagram 58

4.2(a) Transition State 61

4.2(b) Final State 62

4.2(c) Basement Level 63

4.2(d) Request from level three 64

4.2(e) State R3 operation 65

4.2(f) State R4 detected 66

4.2(g) Motor Up/Down off 67

4.2(h) Motor down on 69

4.2(i) State R14 detected 70

4.2(j) Motor down off 71

4.2(k) Door open operate 72

4.2(l) Timer count 73

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4.2(m) Door close operate 74

4.2(n) Sensor Close detected 75

4.3(a) Normally open 77

4.3(b) Normally close 77

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

xiv  

LIST OF SYMBOLS

P - Power

I - Current

V - Voltage

T - Torque

ω - Rotational Speed

F - Force

We - Weight Elevator

Wc - Counterweight

DO - Door Open

SO - Sensor Open

OS - Open Stop

T - Timer

DC - Door Close

SC - Sensor Close

CS - Close Stop

SU - Switch Up

SD - Switch Down

CB - Call Button

R - State

D - Door operation

MU - Motor Up

MD - Motor Down

xv  

LIST OF APPENDICES

APPENDIX TITLE PAGE

A Elevator Motor from the Reuland company 83

B The Project Model 86

CHAPTER 1

INTRODUCTION

1.1. HISTORY OF ELEVATOR

The elevator was first developed during 1800s and relied on steam or hydraulic

plungers for lifting capability. After that, the cab was affixed to a hollow plunger that

lowered into an underground cylinder. Liquid, most commonly water, was injected into the

cylinder to create pressure and make the plunger elevate the cab.

The power elevator debuted mid-19th century in the U.S as simple freight hoist

operating between just two floor in a New York City building. By 1853, Elisha Graves Otis

was at the New York Crystal Palace exposition, demonstrating an elevator with a “safety” to

break the cab’s fall in case of rope failure, a defining moment in elevator development. By

1857, the country’s first Otis passenger elevator was in operation at a New York City

department store.

2  

Later, in the 1800s, with the advent of electricity, the electric motor was

integrated into elevator technology by German inventor Werner von Siemens. With

the motor mounted at the bottom af the cab, this design employed a gearing scheme

to climb shaft walls fitted with racks. In 1887, an electric elevator ws developed i n

Baltimore, using a revolving drum to wind the hoisting rope, but these drums could

not practically be made large enough to store the long hoisting ropes that would be

required by skyscrapers. Motor technology and control methods evolved rapidly. In

1889 came the direct-connected geared electric elevator, allowing for the building of

significantly taller structures. By 1903, this design had evolved into the gearless

traction electric elevator, allowing hundred-plus story buildings to become possible

and forever changing the urban landscape. Multi-speed motors replaced the original

single-speed models to help with landing-leveling and smoother overall operation.

Electromagnet technology replaced manual rope-driven switching and braking. Push-

button controls and various complex signal systems modernized the elevator even

further. Safety improvements have been continual, including a notable development

by Charles Otis, son of original "safety" inventor Elisha, that engaged the "safety" at

any excessive speed, even if the hoisting rope remained intact.

3  

1.2. ELEVATOR

A lift known throughout the world is known as an elevator in the United

States. An elevator or lift is a transport device used to move goods or people

vertically, from one floor to another. The elevator turns electrical power into

mechanical(rotational) power. The elevator must pick up and drop off passenger as

efficiently as possible. If collection of elevator is used, a complex controller usually

controls them. There are many type of elevator or lift depending on the uses of it but

they all work in the same way. These are passenger elevator, freight elevator, vehicle

elevator, boat elevator, aircraft elevator, dumbwaiter, paternoster and others.

A lift/ elevator is made up of 4 major components. The lift/elevator cab or

platform, the shaft or hoistway, the drive system and the counterweight. The cab is

moved vertically using either hydraulic piston or a pulley system. The weight of the

cab is balanced by counterweights so that the drive system uses minimal energy.

The elevator must fit within the given space requirements of the building. It

must be made large enough to deal with the normal daily traffic and to move the

necessary objects within the building. It cannot be made too large and, therefore,

affect the structure of the building itself. Possible restrictions on the weight carried

within the elevator may be determined from the size of the motor and the other

components within the elevator system. This weight limit must be large enough to

handle daily usage.

4  

Figure 1.2(a): Elevator

1.2.1. USES OF ELEVATOR

a) Passenger Elevator

• Designed to move the people between a building’s floors.

• Passenger elevators capacity is related to the available floor space.

Generally, it capacities from 1,000 to 6,000 lb(455-2,727 kg) in 500

lb(230kg) increments.

• Usually, for eight floors or less buildings, hydraulic or electric are

used with speeds up to 200 ft/min(hydraulic) and up to 500

ft/min(electric). But for buildings up to ten floors, electric and

gearless elevator are used with speeds up to 500 ft/min, and for ten

floors above, speeds begin at 500 ft/min up to

2000 ft/min.

• Sometimes, it is used as a city transport along with funiculars.

5  

b) Freight Elevator

• Designed to carry goods rahter than passengers.

• Often exempt from some code requirements anf from some of the

requirements for fire service.

• Generally, it required to display a written notice in the car that the use

by passengers is prohibited, though certain freight elevator allow dual

use through the use of an inconspicious riser.

• It is typically larger and capable of carrying heavier loads than a

passenger elevator, generally from 2,300 to 4,500 kg.

c) Vehicle Elevators

• It is installed where ramps are considered space-inconservative for

smaller buildings(ususally in apartment building where frequent

access is not an issue).

• The car platforms are raised and lowered hydraulically and are

connected to chained steel gears. The platform also can rotate about

its vertical axis (up to 180 degrees) to ease driver access and

accomodate building plans.

6  

d) Boat Elevator

• Used in some smaller canals.

• The boats and small ships can pass between different levels of a

canals with a boat lift rather than through a canal lock.

e) Aircraft Elevator

• It carry aircraft between the flight deck and the hangar deck for

operations or repairs.

• It is designed for much greater capacity than any other elevator ever

build, up to 200,000 pounds of aircraft and equipment.

• Smaller elevators lift munitions to the flight deck from magazines

deep inside the ship.

f) Dumbwaiter

• Often used for the moving of small items such as dishes in a 2-story

kitchen or books in a multistory rack assembly

• Modern dumbwaiters are generally driven by a small electric motor

with a counterweight and their capacity is limited to about 750 lb (340

kg).

7  

• Dumbwaiters are used extensively in the restaurant business (hence

the name) and may also be used as book lifts in libraries, or to

transport mail or similar items in an office tower.

• Dumbwaiters, especially older ones, may also be hand operated using

a roped pulley.

g) Paternoster

• It is a constantly moving chain boxes.

• A similar concept moves only a small platform, which the rider

mounts while using a handhold and was once seen in multi-story

industrial plants.

8  

1.3 PROBLEMS STATEMENT

1. The existing model by De-Lorenzo use a lot of motor in order to operate the

door. It is consist of outside door motor and inside door motor. Each level

have its own motor to open and close the outside door. Therefore, if they have

3 level, they needs 3 motor just for operation of outside door without take

calculation for other use. The other motor that they use is for inside door and

for lift up and down the cab. So, they use 5 motor in that system which is take

more cost.

2. The existing model also not implemented in suitable pulley system. They use

simple types of combination pulley which is not having so much advantage.

That pulley system needs more energy or power in order to lift up and down

the cab.

3. Another problems is, the existing model have limiting level especially in De

Lorenzo model. By this problems, we can’t see the priority of the level in

operation time. In case whenever the cab at the lowers level and there is

signal or call at level 3 and level 5, we can see that it will stop at level 3 fist

before continue to level 5. But for the model where having 3 level, there is

limited to see the cab stop at differential level higher than one.

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1.4. OBJECTIVE OF THE PROJECT

There are two objective of my project which is:

1. To create the model lift controlled by Programmable Logic Control (PLC). This

system is just one of any other system which is attend to be controlled by PLC to

give the overview about what the PLC can do in any system which is related with

our daily life. Automatically, we can see the important use of PLC in its

operation.

2. The other one objective of this project is to create the training kits for students to

give the overview about the real lift operation. Besides, its just not give them

overview about the lift operation, but they also can learn about PLC, how to

setup the system with PLC, how to programming the PLC and others. Therefore,

the students can get a lot of benefits for their knowledge with this training kits.

10  

1.5. SCOPE OF THE PROJECT

The scope of this project involve a mechanical systems, electrical systems

and some programming. There is a lot of combination of electrical and mechanical

parts that are involved compare to the programming because this project is about

create the hardware. The scope of this projects are:

1) Build the lift/ elevator prototypes. The mechanical systems play the

important role in order to build the frame/ body for this project. This

body must have the suitable measurement so that it will have the

stability and strong supporting base. It can’t be very high or low

because it will effect its stability and the supporting base must be

breadth enough to support the lift structure. Besides, this base also

will provide the space for system connection with PLC and the system

circuit.

2) Implement the suitable system. The suitable system is focusing on its

pulley system in order to lift up and down the cab so that it will reduce

the energy and power consumed for that system.

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3) Controlling the lift operation by PLC programming. The brand of

PLC that will be used for this is project is OMRON PLC. This PLC

can be programmed by CX-programming software. All the lift/

elevator operation will be depend on this programe and the error of its

operation will be adjust in this programming. Automatically, the

students will get the knowledge about PLC programming whenever

they use this system kits.

4) Make the circuit connection for the components in the system with

PLC device. The components of this systems would be all the sensor

use, motor, LED indicator, switch and others. By this scope, it involve

understanding of power consumed for each components use and the

method for connection with PLC.

 

 

CHAPTER 2

LITERATURE REVIEW

2.1 DE-LORENZO MODEL

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The De-Lorenzo model [12] consist of real three-stop scaled down lift and

allows an innovative approach to PLC control and management. The model includes:

Lift car up-down and position visual signalling at each floor

Booking to be effected through buttons with flashing signaling, on priority

basis and indepedently from the lift car position.

Lift car geared motor, hoist and electromagnetic brake floor, safety and lift

car deceleration limit switch.

Lift car and floor door open-shut motors.

Motor protection thermal relays simulated by buttons

Lift car deceleration, either up and down, near the stop floor

Reproduction of the inside lift car switch panel

Installation graph on the panel

Connection to PLC through terminals or connection

Fault simulator through microswitch

Power supply, single phase from mains

Complete with connection cables

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2.2. TYPES OF ELEVATOR

There are two main types of elevator which is hyraulic elevator and cable

lifted elevator. One of the different between these two types is the method which it is

lifted and the system that it is used. For the hydraulic elevator, it is lifted from below

by a long metal shaft but for the cable lifted elevator, it is pulled up from above by a

long metal cable. The detail about these types of elevator are:

2.2.1. Hydraulic Elevators

The car/ cab of this types of elevator is lifted from below by a hydraulic ram

which is a long piston that is driven into or out of a hollow cylinder by pressure in a

hydraulic fluid as shown in figure 2.2(a) below. Usually, this fluid is oil or water,

exerts a force on any surface it touches including the base of piston.

“According to John Willey & Sons [1],Whenever the pressure in this hydraulic fluid

is high enough, the force it exerts on the base of the piston will exceed the weight of

the piston and elevator car. Then, it will make the car elevator accelerate upward.”

As the piston rises, the hydraulic fluid has more space to fill and its pressure

drops. In order to keep this piston moving upward, there must be something to

continuously add high pressure hydraulic fluid to the cylinder. This necessity is

usually an electrical powered pump.

15  

It will draws low pressure hydraulic fluid from a reservoir and pumps it into the

cylinder. This pump will work on the fluid and make the elevator car lift.

When the elevator car has reached certain height, the pump stops and the

piston rests on the high pressure hydraulic fluid beneath it. As long as the amount of

this fluid is doesn’t change, the piston and car will stay where the passenger gettin

gon and off. In order to descend, the elevator opens a valve and permits the heigh

pressure hydraulic flu id to return to the low pressure reservoir. The fluid in the

cylinder has considerable pressure potential energy and that energy must go

somewhere. As it flows through the valve, the fluid accelerates and it rushes into the

reservoir at high speed. But its kinetic energy soon becomes thermal energy as the

fluid swirls around randomly. When the swirling has stopped, the fluid in the

reservoir will be warmer than it was before the elevator made its trip up and down.

The hydraulic elevator is naturally safe. Even if the cylinder springs a leak,

the hydraulic fluid will probably not flow out of the cylinder fast enough for the car

to descend at dengeroud speed. a hydraulic ram encounters very little friction and

wear, so its piston can move in or out of the cylinder rapidly.

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Figure 2.2(a): Hydraulic rams

To see how this mechanical advantage works, suppose that you have two

hydraulic rams connected by a hose so that hydraulic fluid can flow freely from one

cylinder to the other, figure 2.2(b). One hydraulic ram is much wider than the other.

Since fluid accelerates toward lower pressure, the pressures in the two cylinders will

tend to equalize. This pressure exerts an upward force on each piston equal to the

pressure times the surface area of that piston. As a result, the upward force on the

wide piston is enough to support the weight of an elevator car while the upward force

on the narrow piston is only enough to support the weight of your hand. As things

stand, neither the elevator nor your hand move because each is supported by pressure

in the hydraulic fluid.

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Now imagine that we begin to push down a little harder on the narrow piston.

The pressure inside that cylinder rises in order to exert an equal but oppositely

directed force on our hand. Because of the pressure imbalance, fluid begins to flow

out of the narrow cylinder and into the wide cylinder. With less fluid in the narrow

cylinder, its piston descends and our hand moves downward.

With more fluid in the wide cylinder, its piston rises and the elevator car move

upward. We are raising a heavy elevator with a hand pump.

Pushing the narrow piston inward a long distance only squeezes a modest

amount of fluid into the wide cylinder. The wide piston moves upward only a very

short distance. We have produced a huge upward force on the elevator and lifted it a

short distance by exerting a modest downward force on the narrow piston and

moving it downward a very long distance. The work we do on the fluid is equal to

the work the fluid does on the elevator car. Energy is conserved, as it must be.

Figure 2.2(b): Two Hydraulic rams

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The piston of the narrow cylinder will reach the bottom long before the

elevator reaches the second floor. To make a more practical hand-powered elevator,

we would need to add several one-way valves and a fluid reservoir to the narrow

cylinder and convert it into a proper pump. That way we could slowly raise the

elevator upward, with ever so many cycles of the pump, fill the narrow cylinder with

fluid and then squeeze it into the wide cylinder, fill the narrow cylinder with fluid,

and so on. To return the wide piston to its original position and lower the elevator, a

bypass valve should allow the hydraulic fluid to flow back

into the fluid reservoir.

“Eventhough the hydraulic elevators are wonderful in many situations, they

do have at least two drawbacks which is stated by John Willey & Sons[1].” First, a

hydraulic elevator is only as tall as its piston and cylinder. The piston has to reach all

the way to the top floor and the equally tall cylinder must be hidden below the

ground. Burying the cylinder is quite a procedure in a tall build. A deep hole must be

drilled and the cylinder must be lowered into the hole with a crane. The difficulties

involved in manufacturing the cylinder and piston and in assembling the completed

hydraulic ram limit itsheight.

However, some hydraulic elevators are over 30 stories tall.The other

deficiency of hydraulic elevators is that there is no mechanism forstoring energy

between trips. The energy expended in lifting people up 30 floors is not saved as

those people descend. It becomes thermal energy in the hydraulic fluid as the

hydraulic fluid returns to the reservoir. For a tall building with lots of up and down

traffic, the elevator can turn a lot of electric energy into thermal energy in the

hydraulic fluid.

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2.2.2. Cabled-Lifted Elevator

In further imrpovement for the safety, the ropes used to lift early elevators

were replaced with metal cables which were less prone to wear and aging and make

cable failure a rare event. With the safety no longer an issue, cable-lifted elevator

soon became the dominant form of elevator.

True cable-lifted elevators resemble the hand-powered one we have just

discussed, except that machines pull the cables. In early cable-lifted elevators, the

cables were pulled by steam-powered hydraulic rams. Steam was used to pump fluid

into or out of the ram and the ram’s movement was used to pull the cables. Usually,

the ram was used to separate the two halves of a multiplepulley. The cable coming

out of this multiple pulley ran over a pulley at the top of the elevator shaft and down

to the elevator car itself. As the two halves of the multiple pulleys were drawn apart,

they drew in more cable and lifted the elevator car. As fluid was released from the

hydraulic ram, the multiple pulley released cable and the elevator car descended.

The first improvement that appeared in cable-lifted elevators was the

counterweight. Lifting the elevator car by itself requires a considerable amount of

work because the car’s gravitational potential energy increases as it rises. It would be

nice to get back this stored energy when the car descends. Unfortunately, it’s hard to

turn gravitational potential energy back into highpressure steam. However, it’s

possible to use that energy to lift a counterweight. The counterweight in an elevator

descends when the car rises and rises when the car descends. Because the two objects

have similar masses, the total amount of mass that is rising or falling as the elevator

moves is almost zero. The overall gravitational potential energy of the elevator is not

changing very much; it’s simply moving around between the various parts of the

machine.

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The counterweight balances the car so that it takes very little power to move the

system. The elevator and counterweight resemble a balanced seesaw, which requires

only a tiny push to make it move.

The counterweight on most elevators hangs from its own cable attached to

the elevator car. That cable travels from the car, over pulleys at the top of the

elevator shaft, and down to the counterweight.

“As stated by John Willey and Sons [1], the counterweight is usually equalto the

mass of the empty elevator car plus about 40% of the elevator’s rated load.”

Thus, when the elevator is 40% filled, the counterweight will exactly balance

thecar and very little work will be done in raising or lowering the car. Most modern

elevators are driven by electric motors. The advantages of electric motors are their

variable speeds of rotation, high torque, and reliability. While we will save our

discussion of electric motors for a later chapter, we will note here that electric motors

can be made to operate efficiently at many rotational speeds, torques, and overall

power-levels. The output power of an electric motor is frequently rated in

horsepower and the motors used in elevators may be as large as several hundred

horsepower.

Because early electric motors could not deliver so much mechanical power,

the first electric elevators used winches to lift their elevator cars. The cable from

the elevator car was actually wound up on a drum at the top of the elevator shaft.

The counterweight was attached to a cable that was also wound on the drum.

The two cables were arranged so that the counterweight cable unwound as the

car cable wound up. An electric motor used gears to turn the drum. This winch

mechanism had a number of disadvantages. It raised or lowered the car relatively

slowly because the gearing limited the rate at which the drum could be turned. The

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overall height of the elevator was limited because the drum had to be able to hold all

of the cable when the elevator was at the top of its travel. The diameter of the drum

was constrained by the need to keep torques low and only about 100 m of cable

could be accommodated.

Instead of winding and unwinding cable from a drum, most modern elevators use

traction to draw a cable over a drum.

The cable rises from the elevator car, travels over the traction drive drum and

then descends into the elevator shaft where it’s attached to the counterweight. An

electric motor turns the traction drive drum. When high speed is not important, the

drum can be turned by a small motor through the use of gears. However, in tall

buildings, the drum is usually turned directly by a large motor. Elevators of this type

can run at speeds as high as 10 m/s (22 mph) in buildings of any height.

The mechanical power required from the drive motor depends on how well

balanced the car and counterweight are. If the elevator car is loaded to 40% of

capacity so that the two weights are balanced, the motor will have little difficulty

in moving the car up or down. If the car is particularly empty or particularly full,

the motor will have to provide considerable mechanical power when lifting the heavy

side of the system and various brakes will have to absorb energy released by the

elevator when the heavy side descends. The motor’s maximum mechanical power,

together with the strength of the cables, limits how much weight the elevator can lift.

In many freight elevators, the car is lifted by a multiple pulley so that a single

segment of cable doesn’t have to support the entire load. Even when a single pulley

is used, several separate cables support the car, both for safety and to reduce cable

stretching. Cable stretching is a serious problem in tall elevators. Tension always

tends to pull things apart, so a cable becomes longer. Like most objects, a cable

behaves as a spring when it’s subject to tension. Its length increases by an amount

22  

proportional to the tension it experiences. As people enter the elevator car and its

total weight increases, the tension on its support cable increases and that cable

stretches slightly. Modern elevators are equipped with automatic leveling systems

that turn the traction drum to make up for the stretching of the cables.

The passengers are unaware of this careful adjustment taking place as they

step on or off the elevator. Nonetheless, we may be able to feel the cable stretch if

you bounce up and down on a cable-lifted elevator.

2.3. BALANCE

“According to John Willey & Sons [1], the elevator cars must remain level no

matter where the passengers choose to stand. The only way to keep the car level is to

make it run along a vertical track.” To see why the track is necessary, consider the

case of an empty car, figure 2.3(a). The lifting force on the car is exerted at the

middle of the elevator car, at either its top or its bottom. The center of mass of the

empty car is also at the middle of the elevator car so the lifting force exerts no torque

on the car about its center of mass. The car remains level. Now consider what

happens when passengers enter the car and begin to walk around inside, figure

2.3(b). The center of mass of the car moves with the people inside. Now the lifting

force exerts a torque on the car about its new center of mass and it tends to rotate.

The best way to prevent the car from tilting is to confine the car on a track. The rails

of the track exert the torques needed to keep the car level.

23  

Figure 2.3(a): Empty car Figure 2.3(b): Occupied car

2.4. SAFETY

All cable-lifted elevators have safety devices to keep them from falling if

their cables break. Most modern elevators have more than one lifting cable, but they

still require mechanisms to ensure that there are no accidents.

The original safety device that Otis developed for his first elevators had

jaws that would grab onto the rails of the elevator track if there were a loss of

tension in the supporting cable. If the cable broke and its tension vanished,

springs would force the jaws into the track.

Modern elevators use mechanisms that monitor the vertical speed of the

elevator. If the speed exceeds a certain permissible value, brakes on the car grab

the tracks. This speed control prevents a nearly empty elevator from moving

24  

upward too quickly just as it prevents a full elevator from falling. One such

speed-sensing device is the centrifugal governor, a mechanism that senses how

quickly a shaft is turning. This is shown in figure 2.4(a) below. When it’s used with

an elevator, the shaft is turned by a pulley on a special cable attached to the elevator

car. The faster the elevator moves, the faster the shaft turns. The centrifugal governor

swings several masses around in a circle. Since the masses travel in uniform circular

motion, they need some centripetal force to accelerate them toward the center of the

circle. In the centrifugal governor, this centripetal force is exerted by several rods

that are held apart by a spring.

As long as the shaft is turning slowly, the spring can keep the rods from

moving together. But when the shaft is turning quickly, the centripetal force becomes

very large and the rods compress the spring. As the rods move, they push

on a lever. In the case of the elevator, this lever activates brakes that slow the

elevator

down.

Figure 2.4(a): Centrifugal governor

25  

A centrifugal governer uses the principle that a central force is required to

accelerate masses around in a circle. As long as the shaft is stopped or spinning

slowly, the spring can keep the upper and lower rods apart. But once the shaft spins

too quickly, the masses swing outward and the sense lever is shifted.

2.5. LIFT PULLEY SYSTEM

There are many ways to lift an object by using the pulley system. But, each

method use have their own advantage compare with others. There are three types of

pulleys which is a fixed pulley, a movable pulley and a combined(compound) pulley.

Fixed Pulley Movable Pulley

Combined Pulley

 

Combined Pulley

26  

2.6. MULTIPLE PULLEY

In a multiple-pulley, the cord goes back and forth between a fixed set of

pulleys and a moving set of pulleys as shown in figure 2.6 (a). The far end is tied to

one of the pulley sets. It’s important that the cord pass easily over the pulleys. Now

when you create tension in the cord, that same tension appears on every segment of

cord between the two sets of pulleys. If you exert 500 N of force on the cord, each

cord segment will have 500 N of tension. As a result, the two sets of pulleys will be

pulled together with 500 N of force for each segment of cord connecting them.

If there are 4 cord segments attached between the top of the elevator and the fifth

floor, then the total lifting force on the elevator and bathtub will be 2000 N. Since the

bathtub and elevator only weigh 1800 N, they will experience a net upward force and

will accelerate upward.

While it takes less force on the cord to lift the bathtub and elevator with a

multiple pulley than with a single pulley, you don’t get something for nothing.

To lift the elevator 1 m, you must shorten each segment of cord by 1 m. Since

there are 4 segments, you will have to pull 4 m of cord through the system of pulleys.

You are obtaining mechanical advantage, using a modest force exerted over

a long distance to obtain a larger force exerted over a shorter distance. The

amount of work required to lift the bathtub and elevator to your apartment is the

same, whether you use a single or multiple pulley. The multiple pulley merely

allows you to do this work more gradually, with a smaller force exerted over a

longer distance.

27  

Figure 2.6(a): Multiple Pulley

2.7. POWER FLOW THROUGH A TYPCAL ELEVATOR:

The simplest theory of operation for pulley system assumes that the pulleys

and lines are weightless and that there is no energy loss due to friction. Its also

assumed that the lines do not stretch. In equilibrium, the total force on the pulley

must be zero which is meana that the force on the axle of the pulley is shared equally

by the two lines looping through the pulley.

28  

The product of the weight lifted times the distance it is moved is equal to the

product of the lifting force (the tension in the lifting line) times the distance the

lifting line is moved. The advantage of the pulley system is defined as the weight

lifted divided by the lifting force.

There is a transfer of power throughout the elevator system. Electrical power

put into the motor is equal to:

(for an AC motor) (2.71)

This power is then transferred through the output of the motor shaft,

(2.72)

.

Where T is the torque and ω is the rotational speed. Once the power is transferred

through the gear reducer the output speed will be reduced and the torque will be

greater. The overall power will be slightly lower as the system is not 100% efficient.

Tension on the rope from the elevator pulley is equal to the weight of the elevator,

We. The tension on the rope from the counter weight is Wc.

29  

Figure 2.7(a): Force on Pulley

By refering to the figure 2.7(a), “the analysis has been done by Rhonda

Salzmon that conclude the force on the driving pulley is equal to the difference of the

two exerted tensions on each side [2].” On one side, this force is equal to We and on

the other side, it is Wc. Therefore, the net force exerted on pulley 1 (the drive pulley)

is:

F = (We – Wc) / 2 (2.73)

In order to find the power required for elevator movement, either the rotational speed

of the drive shaft (attached to pulley 1) or the velocity of the elevator must be known.

The output power is (assumming 100% efficiency),

30  

(2.74)

where r is the radius of the pulley (pulley 1).

Figure 2.7(b): Pulley system implementation

A roping system is used to attach the motor/gear reducer, the elevator car and

the counter weight. There are many different kinds of arrangements that can be used.

In one possible arrangement, such as shown in figure 2.7(b), both ends of the

elevator rope are anchored to the overhead beam. Both the elevator car and the

counter weight are attached to free moving pulleys. The traction drive is attached to a

stationary pulley.

The traction drive is the method of converting the input mechanical power (in

this case the turning of a shaft) into useable mechanical power in the system (the

vertical movement of the elevator). The friction between the ropes and the sheave

grooves, which are cut on the pulley, initiates the traction force between the traction

drive and the rope.

31  

When the traction drive, rotated power is transferred from the traction drive to

the elevator car and counter weight. Power is only needed to move the unbalanced

load between the elevator and the counterweight.

2.8. ELEVATOR OPERATION STATE

2.8.1 Single Elevator

The elevator have three operation states generally. This states are normal

mode, fire-protection mode anf maintenance mode. The most priority is depend on

maintenance mode which have the ability to cancel all the operation.

The second priority is considered to fire-protection mode where it will return

to bottom floor or base immediately in case there is a fire accident. It will goes to

normal mode when the fire switch for the fire-protection mode is reset.

“The basic task for the elevator control system as stated by X.Ying, Q.Zhu &

H.Xu [3] is to command the elevator to move up or down, to stop or start operation,

and to open or close the door. However, for a few case it have some constraints for

example in the case where there is a calling/requests from users in different level.”

The cab will visit the corresponding floor and the illumination is canceled

when the corresponding floor is visited by the cab elevator.

The common elevator has two buttons on the floor control panel except the

first and the top floor to request either to go up or down level.

The elevator cannot stop at a floor unless there is a request from the user. If

there is no request, it will remains at its current floor with the close door.

32  

2.8.2 Two Parallel Elevator

For this system, the basic operation is the same as the system for the single

elevator, but it has the extra operation cause by the related operation of two elevator.

The elevator will test if the stop is required or not depending on the request from the

user.

“According to X.Ying,Q.Zhu & H.Xu [3], to balance the number of stops, the

operation of two elevator will follow a certain dispatching principle. An elevator will

not to stop at a floor if the another elevator was readily stop. In order word, it must

be at least one elevator operate when the another elevator is at the stop operation.

Besides, the first elevator will not to stop at the floor where the second elevator has

been stopped. This level request will make the second elevator to be operate.”

2.9. ELEVATOR MOTOR DRIVE

The types of motor drive used in real elevator system is depend on its

application. For the one to six storey buildings its often use hydraulic elevators. In

this system, it have A/C motors connected to hydraulic pump and work similar to car

lift at service station.

For the low and mid rise buildings, it is most often use geared traction

elevator systems. In this system, the motor drive used is either A/C motor or D/C

motor that is connected to gearbox and then to a drive sheave that moves the cables.

33  

2.9.1 D/C geared motor

For the geared D/C machine, it will typically use either Silicon Control

Rectifier,SCR drive or Motor Generator Set,MGS. The MGS is the older technology

used adn seldomto seen on new installation.

2.9.2 A/C geared motor

In other side, the geared A/C machine will use a Variable Voltage Variable

Frequency,VVVF which can give precise elevator control. The example model of

VVVF A/C geared motor can be refer to the Appendix A. The model is from

Reuland Electric company. The Variable Frequency A/C drives can be divided into

two categories which is inverter drives and flux vector drives. Inverter drives

typically used for low speed and open loop application. The simplest types of this

drives are non-regenerate, where it don’t have teh ability to return regenerated energy

back to the A/C line when overhauling. Regenerated energy must be dissipated

across resistor in the form of heat. For the Flux vectoe drives, it is typically used for

high performance and closed loop applications with speeds above 150 fpm. The

standard os Flux vector drives is also non-regenerative. The resistor is required for

dissipating regenerated energy.

The gearless A/C or D/C machine is used on the most mid to high rise

buildings. For this system, the motor has the drive sheave attached directly to the

motors shaft. The drive systems used for this gearless machine is the same types as

used in the geared machines. “ According to Motion Control Engineering

Incorporated [4], in the most gearless applications, the best choice is D/C machine.

However, if the D/C motor is damaged or defective, the replacing with an A/C motor

will not result in improved performance.”

34  

For the A/C gearless applications, there are two major concern to drives the

decision making process which is heat and cost.

2.10. A/C vs D/C DRIVE EFFICIENCY

Generally, the A/C regenerated drives is the most efficient drive system. This

is because the A/C regenerated drives has unity power factor under all operation

conditions. For a non-regenerative A/C drive, it cannot return regenerated enery back

to the A/C line when overhauling. Instead, this regenerated energy must be

dissipared across resistor in the form of heat.

“ As stated by Motion Control Engineering Incorporated [4], the D/C drives is

more efficient compare to the A/C non regenerated due to the fact that all elevator

D/C drives are regenerative which is capable of returning power back to the power

line.”

Besides, the A/C non-regenerative drives dissipates regenerated energy in the

form of heat into machine room environment. If the air conditioning equipment is

needed to dissipate this energy, it will provide to the loss in efficiency. However, if it

is seen by the issue of power factor, the A/C non-regenerative drive have a closer to

the unity rather than D/C drive which is highly variable for the power factor.

The amount of energy returned during regeneration increses in proportion to

the machine efficiency whether it is a geared or gearless system. For a 30 Horse

Power(30 HP) geared machine regenerated power amount, it could reach 9KW or

more regenerative power in the form of heat at 64% efficiency. In other side, for the

gearless machines, heat dissipation can easily exceed 16KW of regenerative power

for 30 HP motor at 80-90 % efficiency.

35  

2.11. PROGRAMMABLE LOGIC CONTROLLER (PLC)

2.11.1. Introduction

The first Programmable Logic Controller, PLC was developed by a group of

engineers at General Motors in 1968. It was developed when that company were

looking for an alternative to replace complex relay control system. The term

‘programmable logic controller’ is defined by EN 61131-1 as a digitally operating

electronic system which uses a programmable memory for the inernal storage of

user-oriented instructions for implementing specific functions such as logic,

sequencing, timing, counting and arithmetic to control through digital or analogue

inputs and outputs, various machines or process.

PLCs have been gaining popularity on the factory floor and will probably

remain predominant for some time to come. “ The advantage of PLC as stated by Dr.

Hisham El-Sherif [5] are: ”

I. Effective cost for controlling complex systems.

II. Flexible and can be reapplied to control other systems quickly and

easily.

III. Computational ability allow more sophisticated control.

IV. Trouble shooting aids make programming easier and reduce

downtime.

V. Reliable components make these likely to operate for years before

failure.

36  

“ The PLC which is stated by Festo Didactic [5], is represents such a

universal controller where it can be used for different applications and via the

program installed in its memory, provides the user with a simple means of changing,

extending and optimising control process.”

The PLC has sizing into three categories which is small, medium, and large.

The small PLC covers units with up to 128 inputs outputs, I/O and memories up to 2

Kbytes. This PLC’s are capable of providing simple to advance levels or machine

controls. The medium size have up to 2048 I/O’s and memories up to 32 Kbytes. The

larger PLC is the most sophisticated units of the PLC family. They have up to 8192

I/O’s and memories up to 750 Kbytes. It can control individual production processes

or entire plant.

2.11.2. Basic Design of PLC

Figure 2.11(a): PLC design

37  

By refering to the programmaable logic controller, PLC design as shown in

figure 2.11(a) above. The function of each components are:

Function:

1. Input Module - Convert incoming signals into signal which can be

processed by PLC and pass it to central control unit.

2. Output Module - Perform a reverse task of input module. It converts the

PLC signal into signal suitable for the actuators.

3. Central Control Unit -Process the signal accordiing to the program stored in

memory. Its also provides intelligence to command and

govern the activities of thenentire PLC systems.

4. PLC Program - The desired program of sequence of operation and

control instruction which is entered by programmer.

2.11.3. PLC Programming Language

The program of PLC can be created in various ways which is via assembler

type commands in ‘statement list’ (higher level), problems-oriented languages such

as ‘structured text’ or in the form of flow chart which represented by ‘sequential

function chart’. The other programming language that be used are ‘function block

diagram’ based on function charts with graphic symbols and ‘ladder diagram’.

38  

The function block diagrams is widely used in Europe and the ladder diagram is

preferred language by users in America.

Ladder Diagram:

Ladder diagram is the main programming method for PLC. It has been

developed to mimic the relay logic. A relay is a simple device that use magnetic field

to control a switch. When the voltage is supplied to input coil the resulting current

will create a magnetic field. This magnetic field will attract a metal switch toward it

and make it to contact the other part. This programming language is a computer

program where the user can enter and change. For the logic input, there were three

types of input. There are normally open, normally close and immediate input

fuction,IIT. The IIT function allow inputs to be read after the input scan while the

ladder logic is being scanned. The example of these ladder diagram is shown in the

figure 2.11(b) below.

Figure 2.11(b): Ladder diagram input symbols

39  

For the Ladder Logic Output, there are multiple types of outputs but there are

not consistently available on all PLCs. Some of these output will externally

connected to devices outside PLC but its also possible to use internal memory

locations in the PLC. The figure 2.11(c) shows the six type of output which are

normal output, normally on, one short relay (OSR), latch (L), unlatch (U) and the

Immediate output (IOT).

Figure 2.11(c): Ladder diagram output symbols

40  

Sequential Function Chart (SFC):

SFC have been developed to accomodate the programming of more advanced

systems. It is similar to flowcharts but much more powerful. By referring to the

instruction show by the figure 2.11(d), to read the chart, start at the top by says start.

Below this, there is the double horizontal line that says follow both paths. The result

for this instruction will make the PLC start to follow the branch on the left and right

hand sides separately and simultaneously. For the left, there are two functions where

the first is power up function and the second is power down. On the right hand side is

the flash function that will be run until it is done. This method is different from

flowcharts because it does not have to follow a single path through the flowchart.

Figure 2.11(d): Sequental function chart

41  

Structured Text (ST):

Structure text programming has been developed as another modern

programming language. It is quite similar to BASIC language. The example of this

programming language is shown below. In this example, ‘i’ is used as a PLC

memory location for an integer. The ‘RETURN’ is used to recall the value in

location ‘i’. Then it will add by 1 and returns it to the same location. The next line

will check to see if the loop should quit. If ‘i’ is greater than or equal to 10, the loop

will quit but otherwiae the program will go back to the ‘REPEAT’ statement.

Everytime the program goes through this loop, i will increase by 1 untill it reach the

value of 10.

 

CHAPTER 3

METHODOLOGY

3.1 Introduction

Programmable Logic Controller (PLC) play an important function for

this project to control its overall operation. These operation include the instruction

for lift up/down and open/close door. Input from calling button and level sensor(limit

switch) will feed into PLC input module. These input will be send to Central

Processing Unit(CPU) inside PLC to process as required by instruction program. The

instuction program will determine the sequence of operation. After being process by

CPU, it will send the signal as the output to be feed to actuator like motor for this

case. The process diagram is shown in figure 3.1(a) below.

43  

3.2

 

 

 

Hardw

SENSO

LEVEL SENSOR

Figure 3

ware Imple

OR

3.1(a): PLC

ementation

SR

C process dia

LIFT RUCTURE

COMBID PULL

PULLE

agram

E

NELEY

Y SLIDIDOO

NG OR

 

44  

 

 

 

3.2.1 Pulley System

The types of pulley used is combined pulley. For this types, the two

end joint will be hanging or fixed so that it will reduced the power or energy

consumed to lift the cab. The figure and general mathematical model for this

system is shown in figure 3.2(a) below:

Figure 3.2(a): Pulley system

Double side pulley was used for this project to provide stronger tied so that it

can avoid the cab falling down when there is broke up on the rope. The second

side pulley will cover the cab from falling down when the first side has the rope

broken. The example is shown in figure 3(b) below.

45  

Figure 3.2(b): Double side pulley

3.2.2 Sensor

Level sensor was used for this project to detect the level arrived. This

sensor also functioning as the system input to tell the programmable logic

controller(PLC) about the current situation of the system(cab position). The

type of level sensor used for this purpose is limit switch. This is shown in

figure 3.2(c) and the implementation of it is shown in figure 3.2(d) below.

Figure 3.2(c): Limit switch

46  

Specification:

a) Long lever with roller

b) Lever length: 27.5mm

c) Size: 10mm x 28mm x 16mm

Figure 3.2(d): Level sensor implementation

3.2.3 Sliding Door

There are a several components used for this part. The component

used for real sliding door is not provided for prototype uses. Therefore the

implementation for this part come from my creativity that i have so that it will

operate like real sliding door operation. The components used are nilon rope, holding

metal, roller, dc geared motor,limit switch and others. The system implement is

shown in figure 3.2(e) below.

47  

Figure 3.2(e): Sliding door implementation

Limit switch also used for this system to get the information of door position.

When holding metal touch the first limit switch during open door operation, it will

send the signal as the input for programmable logic controller(PLC) to tell that the

door is fully open so that the PLC will give the command according to the instruction

that was programmed. Usually, the instruction for this case is to stop the motor so

that it will not pull the door anymore.

3.2.4 DC Geared Motor

There are two DC Geared Motor used for this project which is for lift

up/down and open/close door. Even this two motor have same voltage capacity (12

volt), but it is different from the the torque and load capacity.

48  

3.2.4.1 DC Geared Motor SPG 50 (12 Volt)

For lift up/down motor, 12 volt DC Geared Motor SPG 50 model from

Cytron company was used. The model is shown below in figure 3.2(f). The

implementation of it is shown in figure 3.2(g).

Figure 3.2(f): DC Geared Motor SPG 50

Specification:

Rated

Voltage(V)

No Load Rated Output

Power

Weight

Current Speed Current Speed Torque

mA r/min A r/min kgf.

cm

mN.

m

W g

12 ≤ 200 225 ≤ 1.1 170 2.0 196 3.4 280

Table 3.2(a): DC Geared Motor SPG 50 specification

49  

Figure 3.2(g): Motor Up/Down implementation

3.2.4.2 DC Geared Motor SPG 20 (12 Volt)

This motor is used to open and close the cab door. It have same rated voltage

as the motor Up/Down but it have its own criteria especially on torque, speed and

output power. This model is shown in figure 3.2(h) below and the implementation of

it is shown in figure 3.2(i).

Figure 3.2(h): DC Geared Motor SPG 20

50  

Specification:

Rated

Voltage(V)

No Load Rated Output

Power

Weight

Current Speed Current Speed Torque

mA r/min A r/min kgf.cm mN.m W g

12 ≤ 30 150 ≤ 200 130 0.6 58.8 0.6 60

Table 3.2(b): DC Geared Motor SPG 20 specifcation

Figure 3.2(i): Open/Close door motor implementation.

51  

3.2.5 Relay

Relays play an important role for most operation. It will determined the

direction of DC Geared motor for both operation (up/down and open/close). Two

relays was used for up/down operation circuit and two for open/close door. When

relay one is turn on by the PLC according to instruction, it will change the polarity so

that the motor will have potential different to make it running in one direction. This

operation also the same when relay two was turning on by PLC in other situation to

make it run in other direction. Single pole double through types of relay was used for

this project with relay voltage of 24 volt. This component is shown by figure 3.2(j)

below.

Figure 3.2(j): Relay

52  

3.2.5.1 RELAY CIRCUIT

Figure 3.2(k): Relay circuit

The circuit in figure 3.2(k) show the relay circuit for up/down cab and

open/close door operation. There are two voltage supply which is from external

supply and from PLC. The external voltage will supply 9 volt fixed voltage for

open/close door motor and 12 volt fixed for up/down motor. In normal situation, the

motor doesn’t have voltage different and will stay until one of the relay change its

polarity to provide voltage different.

53  

3.2.6 OMRON PROGRAMMABLE LOGIC CONTROLLER (PLC)

The programmable logic controller(PLC) is used to control the whole

operation of the system according to the instruction given by the programmer/user. It

is the main part which is give the figure of the electrical controller in that mechanical

system. Without PLC, the system is just a mechanical system which is not operates.

The OMRON SYSMAC CPM2A model PLC is used for this project which is have

22 input and 14 output modul. This PLC is programmed by using Ladder

Diagram(LD) method. The PLC used is shown in figure 3.2(l) below.

Figure 3.2(l): OMRON PLC

54  

There are two PLC used for this project according to limited input output.

Therefore the operation of the system is separate by two part which is lift up/down

for PLC 1 and open/close door operation for PLC 2. To synchronize this two

operation, some of the output from PLC 1 is feed to the input of PLC 2. The output

of PLC 1 is used to give the information to PLC 2 about the current situation so that

PLC 2 will operate as the information given is matching to the instruction that is

programmed.

3.2.7 OTHERS COMPONENTS

3.2.6.1 Counterweight

Counterweight is used to balanced the cab and support drive system so that the motor

will used minimal energy to pull the load. The example is shown in figure 3.29(m)

below.

Figure 3.2(m): Counterweight

55  

3.3 Software Implementation

The software used for programming the programmable logic

controller(PLC). The name of the software used for this project is CX-

Programmer which is used to make the program for OMRON PLC. It

implement the program in the form of Ladder Diagram(LD). The software

used is shown in figure 3.3(a) below.

Figure 3.3(a): CX-Programmer software

Before build the Ladder Diagram, the overall operation is implement in the

state diagram. State diagram will make the operation easily to form in Ladder

Diagram. We cannot easily build Ladder Diagram for the whole operation before

simplify it with state diagram.

56  

3.3.7 State Diagram

For this system, there are two general operation to be controlled by

programmable logic controller,PLC. That operations are lift up/down and open/close

door operation. There is other operation which is on/off indicator but it was included

to up/down operation by using PLC 1. The state diagram for both operation is shown

in the diagram below. The symbols used in this diagram can be refer to list of

symbols in page ?.

Open/Close Door Operation

57  

Lift Up/Down Operation

START 

SU1.SD1

R15.SD1 (CB2 + CB3 + CB4 + CB5).R0.D’.CB1’

R14.CB1.CB2’. D’

R15. MU’ R14.CB1’.(CB3+CB4+CB5) R1.SU2

R1.MD’

(CB3+CB4+CB5).

R13. MU’ R13.SD2 CB1. R2. CB3’. CB4’. CB5’ CB2’. D’. R2

(CB1+CB2). R12. D’. CB3’ R3.SU3

R12. CB2’. CB1’.(CB4+CB5) R3.MD’ R5.MD’

R11. MU’ R11.SD3 R4.CB4’.CB5’(CB1+CB2) (CB4+CB5).CB3’. D’. R4

CB1+CB2+CB3). R10. D’. CB4’ R10.CB2’.CB1’.CB3’.CB5 R5.SU R7.MD’

R9. MU’ R6. CB5’. (CB3+CB2+CB1) R6.CB5.CB4’.D’

R9. SD4

(CB1+CB2+CB3+CB4). R8. D’. CB5’ R7.SU5

Ro 

R1 

R2 

R3 

R4 

R5 

R6 

R7 

R8 

R9 

R10 

R11 

R12 

R13 

R14 

R15 

MU MD 

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3.3.8 Ladder Diagram

CX-Programmer software will implement the instruction program in

the form of Ladder Diagram. The figure 3.3(b) below shown the example of

Ladder Diagram by using the CX-Programmer software.

Figure 3.3(b): CX Progrmmer ladder diagram

CHAPTER 4

RESULT AND DISCUSSION

4.1 Introduction

This project involve hardware and software for support the operation. Mostly,

the focus is given to build the system hardware. The software is used to program the

Programmable Logic Controller, PLC to govern the operation for elevator. Besides,

this programming also can be used to monitor the operation of the system as it is

programmed. The programming used for this project is Ladder Diagram provided by

CX-Programmer software for OMRON PLC. Therefore, the result will be take for

the hardware operation and the programming simulation.

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4.2 Result

4.2.1 Hardware Result

Eventhough this project result will be seen for the system operation, its

operation generally just involved lift up down and open close door. The other

operations like the priority of the calling button or user request cannot be seen by

picture. It will limit our hardware result to showed and can be represented by the

basic operation of the elevator for the request to move up or down and to open or

close the door.

For the lift up and down, the result can be observed that, when the cab have

arrived at certain level, it will touch the sensor level (limit switch for this case). At

this time the sensor will close the circuit and make a current to flow. The current will

be feed to the PLC input as a input signal so that the processor will matching the

information with instruction program to take the action. As a result, the lift motor

will be stopped and turn on the indicator. This result is shown in figure 4.2(a) and

figure 4.2(b) below for transition state and final state operation.

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Lift Up/Down operation:

 

 

 

Figure 4.2(a): Transition State

The PLC will execute the program after receive the input signal and then send

the output signal to the motor. The cab will be moved upward or downward

according to request from or to other level. the transition state operation is shown in

figure 4.2(a) above.

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Figure 4.2(b): Final State

After the cab arrive at certain level (request level), it will touch the level

sensor and feed the signal to the PLC as input signal. The processor wil execute the

program and send the output signal to motor and indicator. If the level is requested

by the user, the PLC will sent the output signal to the motor to make it stop the

operation and to turn on the indicator. The result is shown in figure 4.2(b) above.

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4.2.2 Programming Result

For the CX-programmer ladder diagram, the operation state is shown by the

green highlighting colour. It can provide the monitoring operation without

connecting the PLC with the system hardware to observe the operation. We can

easily simulate the program by using the indicator output in OMRON PLC before

connecting it to the system hardware.

4.2.2.1. Up and Down operation

CASE 1 : The cab at the base level. When there is a calling button from level three,

the instruction will turn ON the motor up,MU and make the cab going

upward. The simulation will show the program running by green highlight.

 

Figure 4.2(c): Basement Level

 

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Transition State R1:

  When there is a call button from level three, the program will run the state

R1. This state will turn the motor up, MU to move the cab. The program running is

shown in figure 4.3(b) below.

 

 

Figure 4.2(d): Request from level three

 

 

 

 

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Level 2 (state R2):

The cab will touch sensor at level two/ state R2. The program will identify

either there is request from this level. If there is no request from this level, the

program will run the next state R3 to turn on motor up, MU to continue the

operation. This running program is shown in figure 4.3(c) below.

 

 

Figure 4.2(e): State R3 operation

 

 

 

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Level 3(state R4):

When the cab touch the sensor at level three, the program will detect the

request and turn off the motor as shown in figure 4.3(d).

Figure 4.2(f): State R4 detected

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If the level is the same as requested by the user, the program will give the

instruction to off the motor. The motor up off is shown by figure 4.3(e) below.

 

Figure 4.2(g): Motor Up/Down off

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CASE 2: The cab is in stop operation at level three. When there is request from

level 1 by the user, the program will run and make the system to

operate.

Request from level 1(CB1) 

 

 

 

 

 

 

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Transition state, R12:

For this state, the program will turn on the motor down to move the cab

downward. The simulation result is shown in figure 4.3(f) below.

Figure 4.2(h): Motor down on

 

 

 

 

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Level 2(state R14): The cab will touch the sensor down for the level two and the

program will identify any request from this level. If there is no

request, the program will execute the next state, R15 to

continue motor down, MD on. The simulation is shown in

figure 4.2(i) below.

Figure 4.2(i): State R14 detected

 

 

 

 

 

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Final state, R0: When the cab touch the sensor down at level one, the program will

turn the motor down, MD off as shown on figure 4.3(j) below.

 

 

Figure 4.2(j): Motor down off

 

 

 

 

 

 

 

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4.2.3. and Close door operation Open

 

CASE 1: Open door operation

When the cab arrive at level 1 and there is request for this level, the program

will turn on the state for door open, DO. The simulation program is shown in figure

4.3(i) below.

Figure 4.2(k): Door open operate

 

 

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Fully Open : When the door touch the sensor open, SO the motor open will turn off

and turn on the timer for a few second (10 second for this case)

before close the door. The simulation program is shown in figure

4.3(j) below.

 

 

Figure 4.2(l): Timer count

 

 

 

 

 

 

 

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Door Close: When the timer is off, the program will turn on motor to close the

door as shown in figure 4.3(k) below.

Figure 4.2(m): Door close operate

 

 

 

 

   

 

 

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Fully Close: When the door touch the sensor close, the program will turn off the

motor to indicate that the system is fully close now. The simulation is

show in figure 4.3(n) below.

 

Figure 4.2(n): Sensor Close detected

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4.3 Discussion

Besides the operation result, its also can be observed that there is other

information that can be find out from the operation. This information will discussed

by the topic below.

4.3.1 Sensor level circuit

The limit switch which is used as a sensor level will initially at normally

open position. After the cab arrive at certain level and touch the limit switch, it will

make the switch to be close and make the current flowing in the circuit. From the

finding, the current flow to the circuit is about 0.08 Amps with 12 Volt supply

voltage. The resistor, R is used to limit the current flow to the circuit. The resistor

value used is 100 ohm.

Power dissipating in resistor, P = I2R

= (0.08)2(100)

= 0.64 Watt

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4.3.2 Relay action

The relay with the 24 volt action voltage is used for this project in up/down

and close door motor operation circuit. After doing some test to this relay, when the

voltage is varried from 0 volt to 24 volt voltage supply, the relay turn on when it is

supplied by plus minus 15 volt supply voltage. The relay will be in normally open as

shown in figure 4.3(a) for 0 – 14 volt supply voltage and will be close for the voltage

above 15 volt as shown in figure 4.3(b) below.

Figure 4.3(a): Normally open Figure 4.3(b): Normally close

 

CHAPTER 5

CONCLUSION

5.1 CONCLUSION

From the objective of this project, we can see that the knowledge and skills

will combined together in order to complete this task. For this project, the

knowledge and skills that involve is not depending to electrical system but its also

involve the mechanical system. Without relation of each part, the system will having

the problems and this project cannot completely finished.

Besides, in this project, its also will give the challenges to students for having

the knowledge and understanding in other field besides the electrical knowledge.

Automatically, it will train the students in solving the problems eventhough it is

outside of their field of study.

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From the objective of this project also, it will give a lot of knowledge which

is involved especially in PLC control system. Indirectly, from this project, the

students just not learn in controlling the system, but they also can learn about

programming the PLC in order to running the system. The students also can get the

creativity skills in programming the PLC so that it will running with their own way

operation.

5.2 Problems

Eventhough the system use two programmable logic controller, PLC because

of its limited input output, I/O, its still have the problem to communicate the first

PLC with the second PLC. This communication of these PLC is needed to ensure

that the system operate synchronously between the open close door operation and up

down operation.

Besides, there are over current from the sensor level circuit that make the

resistor burn after the current flow for long time. After that the signal from the

sensor cannot be detected and cannot sense the current position of the cab anymore.

When the sensor can’t be detected, the program cannot run the operation because it is

depend on the position of the cab.

The design also is the one problems that limited the space to installed extra

component like IR sensor to used as the safety. It should have the sensor to detect the

user that want to enter or go out to from tthe cab as a safety equipment so that the

user can’t be hitted by the door.

` There is no breaking system installed for this prototype due to limited time

for finishing the project. The breaking system is used as a safety in case the cable is

broken to avoid the cab falling down with the high speed.

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5.3 Recommendation

The efficient operation can be achieve when there is enough Input Output for

all the component used in this system. We can use the medium size of PLc to provide

enough input output, I/O.

There is a sensor that can use as a safety in the sytem so that the user will not

hitted by the door during the entering and out of the cab. The Infrared sensor can be

used as the one of the suitable sensor that can detect the movement through the cab.

We can used the fius in the circuit to avoid the the current overflow and make

resistor burn. The fius can be instaled in each circuit so that when there is a overload

current flow, it will shot the fius without effectinh other equipment.

The breaking system should be installed for one of the safety requirement to

avoid the excident when there are problems with the cable used in drive system.

Besides, for this case we can overcome the excident by make the program to give the

instruction to either stop the operation at close level to the current position.

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REFERENCE

1) John Willey (2001). Elevator. London: John Willy & Sons. 1-8

2) Rhonda Salzmon (1998 & 1999). How Elevator Works: Martin L.

Culpepper. 1-3

3) X.Ying, Q.Zhu, H.Xu (2008). Design and Practice of an Elevator

Control System Based on PLC: IEEE, DOI 10.1109/PEITS: 94-96

4) Motion Control Engineering Incorporated (March 1999). AC Motor

Controls for Elevators: Motion Control Engineering Incorporated.

5) FESTO Didactic (2002). Programmable Logic Controller Basic Level.

(TP 301).

6) Dr. Hisham El-Sherif. Basic PLC. Industrial Park: GUC. 5-33; 2001

7) G.C Barney (1986) “ Elevator Technology”, Chister : Elis Honwood.

8) G.C Barney (1935) “ Elevator Traffic Handbook” , London : Taylor &

Francis, 2003

9) Janovsky, Lubomir “ Elevator Mechanical Design” 2nd Edition, New York :

Ellis Horwood, 1993

10) Lemony Snicket “ The Ersatz Elevator” , HarperChildren’s Audio, August

1st 2003.

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11) http://en.wikipedia.org/wiki/Elevator (10/9/2008: 2130)

12) http://www.delorenzo.it/dl/eng/prodotti-en/automazione-en.htm

(15/9/2008: 2200).  

13) http://howthingswork.virginia.edu/supplements/elevators.pdf

(15/9/2008: 2230).

14) http://www.columbia-elevator.com/info/history.html              

(15/9/2008: 2245).

 

 

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APPENDIX A

Elevator motor from the Reuland company

VVVF A/C motor by Reulend Electric Company:

 

 

 

 

 

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Single Speed A/C Elevator Motor (Reuland Electric company):

 

 

Specification

85  

Two Speed A/C Elevator Motor (Reuland Electric company):

Specification

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APPENDIX B

THE PROJECT MODEL

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CONTROL PANEL

ELEVATOR CAB