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CHAPTER NO: 1

INTRODUCTION

A traction control system (TCS), also known as Anti-slip regulator (ASR), is typically(but not necessarily) an electro-hydraulic system on production vehicles designed to

prevent loss of traction of the driven wheels, and therefore maintain the control of the

vehicle when excessive throttle is applied by the driver and the condition of the road

surface (due to varying factors) is unable to cope with the torque applied. Although

similar to the to the Electronic stability control (ESC) systems, traction control systems

do not have the same goal.

1.1 History

The predecessor of modern electronic traction control systems can be found in high-

torque, high-power rear-wheel drive cars as limited slip differential, Limited slip

differential is a purely mechanical system that transfers a relatively small amount of

power to the non-slipping wheel, it still allows some wheel spin to occur.

In 1971 the Buick division of GM introduced Max Trac, which used an early computer

system to detect rear wheel spin and modulate engine power to those wheels to provide

the most traction. A Buick-exclusive at the time, it was an option on all full-size models,

including the Riviera, Estate Wagon, Electra 225, Centurion, and popular Le Sabre family

sedan. Cadillac also introduced the ill fated Traction Monitoring System (TMS) in 1979

on the redesigned Eldorado. It was criticized for its slow reaction time and extremely high

failure rate.

1.2 Basic Idea

The basic idea behind the need of a traction control system is the difference between the

slips of different wheels or an apparent loss of road grip that may result in loss of steering

control over the vehicle. Difference in slip may occur due to turning of a vehicle or



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differently varying road conditions for different wheels. At high speeds, when a car tends

to turn, its outer and inner wheels are subjected to different speed of rotation that is

conventionally controlled by using a differential. A further enhancement of the

differential is to employ an active differential that can vary the amount of power being

delivered to outer and inner wheels according to the need (for example, if, while turning

right, outward slip (equivalently saying, 'yaw') is sensed, active differential may deliver

more power to the outer wheel, so as to minimize the yaw (that is basically the degree to

which the front and rear wheels of a car are out of line.) Active-differential, in turn, is

controlled by an assembly of electromechanical sensors collaborating with a traction

control unit. The graph 1.1 shown below shows a typical curve which determines the slip

ratios for different surfaces here the slip ratio varies according to the coefficient of

friction. Here it is observed that as the coefficient of friction increases the slip-ratio also

decreases up to a certain limit then afterwards it remains nearly constant afterwards.

Graph 1.1 Coefficient of friction v/s slip ratio



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1.3 Methods of traction control system

y B speed cont ol of t e wheels

1. B cutting the fuel in jector¶s

2.

B appl ing brakes through TR C B ECU y R etard or suppress the spark in the cylinders

y To reduce the fuel supply in the combustion chambers

y In case of turbocharged vehicles reducing the power by activating Boost control

solenoid valve.

y Electronic Throttle control of the engine

Traction controlsystems

Wheel sped type

control systems

Engine type

control system

Mission type (yaw rate

control Method)



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CHAPTER NO: 2

CUTTING FUEL INJECTOR¶S

In this type the traction control is completed by joint efforts of the ABS-TRAC EC &

ECM when the slip occurs the slip of the wheel is detected by the ECM and one of the

cylinders is cut-off by cutting of the injector ultimately reducing the total power produced

by the engine. Once the slippage of the wheels stops then the, the cut-off injector is again

activated, thus the engine again starts producing maximum power.

2.1 Components of the ³fuel injector type system´

a) Wheel speed sensors

b) TRAC pump

c) Solenoid valves

d) TRAC actuator

2.2 Operation

The operation of ³cutting the fuel injector´ type of system is carried out by the ECM of

the automobile. When the speed of the wheels increases the control starting speed then

the wheel speed sensors senses it & sends signals to the ECM, the ECM cuts-off few

injectors, when the speed of the wheel decreases some of the injectors are again

connected, only some injectors are connected to avoid overshooting of the wheel speed

then once the control speed is attained then finally all the injectors are connected to the

engine, thus the engine starts producing maximum power. This is the most simplest of the

all traction control systems, the biggest disadvantage of this kind of control system is that

this system can only be implemented in case of more than 5 cylinder engines.



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CHAPTER NO: 3

BY APPLYING BRAKES THROUGH ABS-TRAC ECU

The ABS/TRAC EC work together, the wheel speed sensor senses the wheel speed

ultimately the speed of the vehicle, then the EC controls the brake of the automobile

ultimately the speed of the engine.

3.1 Components of ³Brake type speed control Traction control unit´

y Solenoid valves 12nos. (2 Master cut-off , 2 Reservoir cut-off, 8 Pressure

regulator)

y TRAC pump

y TRAC actuator

y TRAC EC (electronic control module)

y Wheel speed sensors

y Display unit

3.2 Operation

There are modes of operation in a ³brake type wheel speed control system´ they are as

follows

1. Normal mode of operation

2. Pressure increase mode

3. Pressure holding mode

4. Pressure reduction mode.



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3.2.1Normal mode of operation: When the traction control system is not activated

at all actuator valves are OFF. The Master cut solenoid valve is open allowing the fluid

from master cylinder to flow to the pressure holding valve to the brake cylinder. In this

type the brake just works as that of the system without ABS/TRAC.

(Refer Figure No.3.1)

Table no: 3.1 Normal mode of operation

Part Name Signal from

ABS&TRAC ECU

Operation

Master Cut solenoid Valve OFF Port B Open

Reservoir Cut Solenoid Valve OFF Port H Closed

Pressure Holding Mode OFF Port C Open

Pressure Reduction Valve OFF Port F Closed

Pump OFF Stop

3.2.2 Pressure increase mode: During sudden acceleration or driving on slippery

roads, if the drive wheel suddenly starts to slip the ABS/TRAC EC forces the TRAC

actuator to go into pressure increase mode. The Master solenoid is ON blocking the brakecircuit to the Master cylinder, the reservoir solenoid is open connecting the Master

cylinder to the TRAC pump, the pump is turned ON thus increasing the brake fluid

pressure the pump is connected to the pressure holding valve then to the brake cylinder.

(Refer Figure No. 3.2)

Table no: 3.2 Pressure increase mode

Part Name Signal from

ABS&TRAC ECU

Operation

Master Cut Solenoid valve ON Port B Closed

Reservoir Cut Solenoid Valve ON Port H Open

Pressure Holding Valve OFF Port C Open

Pressure Reduction Valve OFF Port F Closed

Pump ON Rotating



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3.2.3 Pressure holding mode: When fluid pressure in the wheel cylinder circuit is

optimized by an increase or decrease in pressure, the ABS/TRAC EC controls the

system as follows, the pressure holding valve is turned ON blocking the pressure from the

pump, the reservoir cut solenoid valve is turned OFF blocking additional fluid from the

reservoir, though the pumps keeps rotating.


Table No: 3.3 Pressure holding Mode

Part Name Signal From ABS

TRAC ECU

Operation

Master Cut Solenoid Valve ON Port B Closed


Pressure Holding Valve ON Port C Closed

Pressure reduction valve OFF Port F Closed

Pump ON Rotating

3.2.4 Pressure reduction mode: When the fluid pressure inside the cylinder is to be

reduced, Reservoir solenoid is turned OFF and the spring loaded valve is kept in theclosed position blocking the fluid from the master cylinder to the pump, Master is cut

from the brake cylinder by turning on the Master cut solenoid valve, the pressure

reduction valve is turned ON, hence reducing the pressure of the brake fluid entering the

brake cylinder.


Table No:3.4 Pressure Reduction Mode

Part Name Signal from ABS &

TRAC ECU

Operation

Master Cut Solenoid Valve ON Port B Closed


Pressure Holding Valve ON Port C Closed

Pressure Reduction Valve ON Port F Open

Pump ON Rotating



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CHAPTER NO: 4

THROTTLE VALVE CONTROL SYSTEM

This system is similar to the speed control system the differences are that in this a sub-

throttle actuator is used in front of the throttle valve to control the torque produced by the

engine & there is no brake actuator present in this system.

4.1 Components of ³Throttle valve control traction control system´

y Sub-throttle valve motor

y Sub-throttle position sensor

y Throttle valve

y Acceleration Position sensor

y TRAC ECM (electronic control module)


4.2 Operation:

As the accelerator pedal is pressed & when the wheel speed is below 40km/hr the

Acceleration sensor sends signal to the ECM, Whereas simultaneously the Throttle

position sensor sends electronic signals regarding the current position of the throttle

valve, The ECM evaluates the signals received from the sensors and decides the new

required position of the throttle valve and sends signals to the throttle motor to control the

throttle position accordingly. When the slip-ratio is again slowly coming back within the

tolerable limits then the throttle valve is again gradually opened by EC & finally when

there is no slip then the throttle valve operates normally. This kind of system is very

useful in Electric vehicles.

This system is the most widely used system of all the different types of traction

control systems.




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4.3 Fail safe operation

The Electronic Throttle Control System has multiple built-in fail-safes and diagnostic

capabilities. If the Electronic Throttle Control System detects a malfunction, the ECM is programmed to initiate a fail safe mode. The following are some examples:

1. If one Accelerator Position Sensor fails, the ECM will illuminate the ³Check

Engine´ light, store diagnostic service information, and limit throttle opening to

about ¼, allowing the vehicle to be driven at reduced power.

2. If both Accelerator Position Sensors fail, or if one Throttle Position Sensor fails,

the ECM will Illuminate the ³Check Engine´ light, store diagnostic service

information and cut power to the throttle, returning the engine to idle speed.

3. If the Throttle Valve binds, the ECM will Illuminate the ³Check Engine´ light,

store diagnostic service information and shut the engine off.



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CHAPTER NO: 5

MISSION TYPE CONTROL SYSTEMS

The mission type control system is a type of traction control system in which the torque

of the slipping wheel is transferred to the non-slipping wheel. Here this is achieved by

braking one of the wheels and simultaneously accelerating other wheel, this kind of

system is very efficient in controlling the yaw-rate, thus can be very effectively used for

avoiding accidents occurring due to slippage of wheels due to under steering or over

steering of wheels at high speeds due to a sudden obstacle on the road. This type of

system is often also known as ESP (electronic stability program) OR ESC (electronic

stability control). Different manufacturers use different nomenclatures to designate this

system, but the functioning of the system is basically the same.

5.1 Components of Mission type Traction control system

y EC (electronic control unit)

y µYaw rate¶ or lateral acceleration sensor

y Steering angle sensor

5.2 Operation

The ESC is active 25 times a second (i.e.) the frequency of the ESC is 25. It compares the

whether the drivers the steering input corresponds to the actual direction of the vehicle in

which the vehicle is moving. If the vehicle moves in direction other then the desired

direction (i.e.) if the vehicle over-steers or under-steers ESC detects critical situation and

reacts accordingly, to do this it uses the vehicle brakes and the throttle, so the mission

type control system is an combination of both the brake type and throttle control type

traction control systems. Specific braking intervention is directed at individual wheels,

such as the inner rear wheel to counter under steer, or the outer front wheel during over

steer. These selective braking interventions generate the desired counteracting force.

ESC not only initiates braking intervention, but can also intervene on the engine side to



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accelerate the driven wheel. There are basically two types of modes or mechanism¶s in-

volved in the operation of the Mission type of traction control system they are

1. Under steer mechanism

2. Over steer mechanism.

(Refer Figure No¶s. 5.1, 5.2)

5.2.1 Under steer mechanism

When a driver takes a hard turn during cornering if the vehicle under steers the steering

angle sensor senses the under steer of wheel it sends signals to the control unit, the

Control unit brakes the inner wheel and simultaneously accelerates the outer front wheel,

So the mission type traction control system is a combination of both brake type as well as

throttle type control system.

(Refer fig No. 5.3)

5.2.2 Over steer correction mechanism

When a driver is trying to avoid an obstacle on the road if he over steers and slippage of

wheels occurs the steering angle sensor senses the over steer the yaw rate sensor senses

the slippage of wheels and it sends signals to the control unit. The control unit controls

the slippage of wheels, by braking the outer rear wheel and simultaneously accelerating

the inner front wheel.

(Refer fig No.5.4)



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CHAPTER NO: 6

BENEFITS & COMPARISONS

6.1 Benefits

Car accidents dominate the transportation industry in regards to the number of deaths that

occur on the road, accounting for 94 percent. With over half a million car wrecks every

year, safety aspects, such as traction control, are being constantly developed to keep

drivers safer. By understanding modern-day safety features, drivers can stay well-

informed of potential aftermarket options for their vehicles to keep them safe.

Goal

1. The traction control system is a relatively modern safety tool. An alternative to

4WD and AWD---the common drive train systems that still dominate the market---traction control works on 2WD vehicles by helping to provide more protection in

dangerous weather, where lack of traction can become dangerous. The majority of

traction control systems work by detecting slips in any of the wheels---a common

occurrence in bad weather---followed by the application of brake pressure to the

wheel that is slipping. Some traction control systems can cut engine power back as

well, to avoid an increase in the amount of spin that the wheel is producing. By

applying pressure to the slipping wheel, power is sent to the drive wheel with the

most grip-restoring control in many cases.

Testing

2. The major concern for most drivers that are thinking of switching their drive train

system, or thinking of purchasing a car with a traction control system, is the

amount of testing that has been done. Traction control systems are built for

durability and created to handle the variable requirements of multiple types

of cars. The system can withstand over 4500 psi on your braking diaphragm and

even has a second seal---ensuring no pressure loss occurs even if the brake

diaphragm fails.

Affordability

3. Traction control systems are a much cheaper, alternative drive train solution for

drivers due to their ability to be manufactured at lower prices.



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Responsiveness

4. Since traction control is a change in your braking system, a change in the feel of

your brakes will occur. Traction control brakes are softer, rather than being

extremely sensitive; however, if you brake hard, you will feel the responsiveness,

just as you would with traditional anti-lock systems that are found on other 4WD

and 2WD vehicles.

6.2 Comparison

Table no: 6.1 Comparison between traction control systems

CONTROLLABILITY

RESPONSE COST

OPERATING

FEEL TOTAL

ENGINE

CONTROL GOOD FAIR EXCELLENT FAIR GOOD

BRAKE

CONTROL GOOD EXCELLENT EXCELLENT POOR FAIR

MISSION

CONTROL FAIR POOR EXCELLENT FAIR POOR





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CHAPTER: 8

CONCLUSION

From the above presentation it can be said that power can be saved by using a traction

control system in an automobile& slippage of an automobile can be avoided during fast

cornering very effectively. Out of the various types Traction control systems studied the

engine type traction control system was found to be most effective type of traction control

system. Due to some practical difficulties faced in the implementation of this kind of

system in automobiles. So brake type traction control system is preferred over the other

types of systems and this type of system is widely used in different automobiles.

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