tractioncontrolsystem (1)

TRACTION CONTROL SYSTEMS

A SEMINAR REPORT SUBMITTED IN PARTIAL FULLFILLMENT OF

THE

REQUIREMENTS FOR THE AWARD OF

BACHELOR OF TECHNOLOGY

IN

MECHANICAL ENGINEERING (MECHATRONICS)

By

SRINIVAS PAREEK

(08261A1460)

DEPARTMENT OF MECHANICAL ENGINEERING (MECHATRONICS)

MAHATMA GANDHI INSTITUTE OF TECHNOLOGY

(Affiliated to Jawaharlal Nehru Technological University, Hyderabad)

Accredited by National Board of Accreditation, New Delhi

Gandipet, Hyderabad-500075(A.P.)

www.mgit.ac.in

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TABLE OF CONTENTS:

Sl. No. Title Page No.

1. Abstract 03

2. Introduction 04

3. History 05

4. Literature survey 06

5. Block diagram of traction control system (TRAC) 07

6. Working of traction control system 09

7. Case studies 10

8. Scope 11

9. Summary of review 13

10. TRAC system components of Toyota supra mark

IV

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11. TRAC wheel speed control 17

12. Benefits of traction control 18

13. Applications 21

14. Safest Traction Control Cars 23

15. Conclusion 25

16. References 26

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ABSTRACT:

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. Traction Control Systems is the

modern day solution to the problems such as unnecessary skids power loss

due to less traction and railway track traction control. Whilst the old methods

such as limited slip differentials are getting inefficient to handle the critical

driving situations, need for a more advanced traction control system arises

and henceforth comes into picture the Electronic Traction Control System or

the TRAC System.

This paper puts light to the modern Traction Control system basics,

working, benefits and applications while appreciating the history of the

traction control systems and present world utilizations.

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INTRODUCTION:

Traction refers to the maximum frictional force that can be produced

between surfaces without slipping. In auto mobiles traction is responsible for

the movement of vehicle. In the design of wheeled or tracked vehicles, high

traction between wheel and ground is more desirable than low traction, as it

allows for more energetic acceleration without wheel slippage.

Traction control is a technology designed to help your vehicle

maintain traction, no matter how slippery the road surface. Technically, it is

a mechanical, hydraulic, or electric system that maintains or controls traction

to any wheels driven by the engine. Unlike mechanical traction control

systems of the past such as limited slip differentials, today’s systems are

nearly all computer-controlled as they actively watch wheel slip. An option

formerly reserved for performance, you can find traction control on all types

of vehicles today.

The purpose of the Traction Control System is to prevent wheel spin

from occurring due to acceleration. The maximum torque that can be

transmitted to the wheels is determined by the coefficient of friction

generated between the road and the tires. If torque exceeds that level, the

wheels are likely to spin. Conditions for Traction operation may include

slippery road surfaces, acceleration while cornering and hard acceleration.

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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 which leads to

slipping of the vehicle and loss of power which results in uncontrolled

cruising. Difference in slip may occur due to turning of a vehicle or

differently varying road conditions for different wheels. And thus need to be

controlled for a safer way to cruise.

HISTORY:

Traction has always been the Achilles Heel of any vehicle. A perfectly

capable car or truck becomes completely useless when stuck in sand, mud, or

snow. Early in the development of the modern motor vehicle, engineers

realized that 4-wheel drive (4WD) was one answer. By sending engine

power to all four wheels, at least one wheel would have enough grip to pull

the vehicle through. It was a brilliant discovery, but 4WD meant that the

vehicle would have to carry extra weight, complexity, and suffer the

increased fuel consumption associated with the 4WD drive train, even when

it was not in use.

Traction control system uses a form of technology designed for

aircraft in the 1950s called anti-lock brakes, or ABS. Aircraft engineers

developed a system of mechanical sensors to measure and detect when a

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wheel was skidding and hydraulically release the braking force on that

wheel. With an ABS system, an aircraft could apply brake with maximum

stopping power without skidding, regardless of weather conditions. With

further development, automotive engineers realized they could “reverse” the

operation of the ABS to build an effective traction control system using the

same sensors.

One hundred years after the development of the automobile,

microcomputer technology has finally solved the traction puzzle. In 1987,

the earliest innovators of automotive vehicles, Mercedes-Benz and BMW,

introduced their first traction control systems. Traction Control was first

introduced on the 1994 Turbo Supra and expanded to include the six cylinder

Camry and Avalon models in 1997.

Recently in the motorsport sector traction control system is given a red

flag by International Automobile Federation as it banned use of traction

control in races effective from 2008. Apart from that when it comes to

performance and safety, Traction control system dominates the world

automobile sector.

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LITERATURE SURVEY:

BLOCK DIAGRAM OF TRACTION CONTROL SYSTEM

(TRAC):

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WORKING OF TRACTION CONTROL SYSTEM:

A simple input output process block diagram is given in figure 1 and

various inputs are shown on the left side. The process control unit is

represented in the middle part if the figure. Right side blocks of the diagram

shows the various controlled outputs for the TRAC system.

The main inputs for a TRAC system are wheel speed sensors, battery

level sensor, TRAC OFF switch, stop light switch, and the throttle position

sensor. These inputs give speed signal, remaining battery signal, OFF signal,

stop signal and throttle level signal respectively.

The processing part consists of an Anti-lock Braking System (ABS) or

a TRAC Electronic Control Unit (TRAC ECU) and an Engine Control

Modulator (ECM). The TRAC ECU will have an interconnection with ECM

in order to communicate to the engine throttle position control. These

processing units process and analyze the input signals and take necessary

output actions if required.

The controlled outputs of a TRAC system are solenoids actuator,

pump motor actuator, slip indicator light, TRAC OFF light, ABS warning

light, injectors control, and solenoid valve actuator.

The control action can consist of one or more actions such as reducing

or suppress the spark to one or more cylinders, reducing fuel supply to one

or more cylinders, brake one or more wheels, close the throttle where vehicle

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is fitted with ECM controlled throttle, and the boost control solenoid can be

actuated to reduce boost and therefore engine power. The controlled action

of the one or more of the above outputs can help in traction control of the

vehicle resulting in a slip proof cruising of the vehicle irrespective of the

external weather conditions.

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FACTS:

1. The predecessor of modern electronic traction control systems can be

found in high-torque, high-power rear-wheel drive cars as a limited

slip differential. Limited slip differential is a purely mechanical

system that transfers a relatively small amount of power to the non-

slipping wheel, but it still allows some wheel spin to occur.

2. In 1971 the Buick division of GM introduced MaxTrac, 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 LeSabre

family sedan.

3. Traction control for a production motorcycle was first available with

the Honda ST1100 in 1992. By 2009, traction control was an option

for several models offered by BMW and Ducati, and the model year

2010 Kawasaki Concours 14 (1400GTR).

4. Mitsubishi's modern Active Skid and Traction Control (ASTC) system

which was developed to help the driver maintain the intended path

through a corner, an onboard computer monitored several vehicle

operating parameters through the use of various sensors.

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5. In the design of wheeled or tracked vehicles, high traction between

wheel and ground is more desirable than low traction, as it allows for

more energetic acceleration including cornering and braking without

wheel slippage. One notable exception is in the motorsport technique

of drifting, in which rear-wheel traction is purposely lost during high

speed cornering.

SCOPE:

Spinning the tires not only makes the car harder to drive, but it also

causes higher tire temps and excessive tire wear. Lifting off the throttle or

counter steering to correct for this 5% mistake, not only upsets the rhythm, it

slows the car down. Typically, if a driver makes a 5% mistake with the

throttle, he/she has to correct 20-25% to fix it. But if the tire slip is detected

within one cylinder worth of crank rotation, as the Davis Technologies

systems do, then a small reduction in power can reduce or stop the tire slip.

The Non Self-Learning systems, such as Traction Maintenance

System (TMS), periodically compare the rate of acceleration of the

crankshaft to an Adjustable Fixed Rate (AFR), known as Threshold. If the

Engine RPM rate of change is in excess of that Threshold, then a correction

is made; therefore, reducing the slip.

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Basically, the TRAC system looks for spikes in RPM that are caused

by wheel slip.  If these spikes are large enough, then a correction is made,

reducing the slip. By adjusting the Threshold, the driver can tune the system

to the desired "feel".

Self-Learning systems, such as our TMS-750-SL, TMS-5500-SL, and

TMS-9500-SL series, which were introduced by Davis Technologies, can

compare the rate of acceleration of the crankshaft to a calculated threshold

value that is constantly updated based on the average of the previous

measurements. This update occurs on every crankshaft revolution.

Through this very advanced control process, the system constantly

accounts for track conditions, tire condition, even driving style to constantly

update the internal settings. These settings are updated as many as 200 times

a second to keep the unit calibrated to exactly the right settings regardless of

changing conditions. This allows the system to adjust to the correct settings

even if one corner has more grip than another or one grooves to another.

The user does have an adjustment referred to as “Mode” that sets the

overall sensitivity of the system to make a correction based the extent of the

tire slip.  By adjusting the Mode, the driver can tune the system to the

desired TRAC control level.

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The speed and learning capabilities of these systems is what makes the

best traction control on the market today.  Allowing you to focus on chassis

set-up, and not be distracted by constantly having to adjust your traction

control settings, as with systems that work on a percentage of slip between

the front and rear wheels.

SUMMARY OF REVIEW:

Traction control helps limit tire slip in acceleration on slippery

surfaces. Powerful rear-drive cars from the sixties often had a primitive form

of traction control called a limited slip differential helping to reduce, but not

eliminate wheel spin. While limited-slip rear axles are still in use in many

front- and rear-drive vehicles today, the device can't completely eliminate

wheel slip. Hence, a more sophisticated system was needed.

Enter electronic traction control. In modern vehicles, traction-control

systems utilize the same wheel-speed sensors employed by the antilock

braking system. These sensors measure differences in rotational speed to

determine if the wheels that are receiving power have lost traction. When the

traction-control system determines that one wheel is spinning more quickly

than the others, it automatically applies brake to that wheel to reduce its

speed and lessen wheel slip. In most cases, individual wheel braking is

enough to control wheel slip. Therefore for drivers who routinely drive in

snowy and icy conditions, traction control is a must-have safety feature.

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TRAC SYSTEM COMPONENTS OF TOYOTA

SUPRA MARK IV:

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Fig 2

The Toyota Supra is a sports car that was produced by Toyota Motor

Company from 1979 to 2002. It introduced TRAC system in model “Supra

Mark IV” in the year 1994. It was most notable is the separate TRAC

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actuator and ABS actuator in 1993 till 1995. Engine torque is controlled via a

sub-throttle actuator which controls the sub-throttle ahead of the valve in the

throttle body.

The TRAC System reduces engine torque and rear wheel speed as

necessary to bring the vehicle under control. The ABS ECU, TRAC ECU and

ECM all work together to provide traction control. ABS speed sensors are

monitored by the TRAC ECU which in turn controls a sub-throttle plate and

applies the rear brakes. The ECM also retards engine timing while the ABS

modulates pressure at the rear brakes.

The supra TRAC system is represented in figure 2 of previous page.

The TRAC OFF switch is located on the instrument panel above the center

console. It allows the driver to activate or deactivate the TRAC system when

the switch is depressed. The system defaults to ON when the ignition switch

is cycled.

The Sub-Throttle Actuator uses a step motor located between the main

throttle valve and air cleaner. It is fitted on the throttle body and controls the

position of the sub-throttle valve based on commands made by the TRAC

ECU thus controlling the engine output.

Sub-Throttle Position sensor is fitted to the sub-throttle valve shaft. It

converts the sub-throttle valve opening angle to a voltage signal and sends

this signal to the TRAC ECU via the ECM (Engine ECU). The sensor is built

and operates in the same way as the main Throttle Position Sensor.

Apart from the above explained components all the remaining

operational components work in the same way that of explanation to the

block diagram of TRAC system

TRAC WHEEL SPEED CONTROL:

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Fig 3

Figure 3 shows a graph of wheel speed control against time taken to

control. It is basically representing the accuracy of the TRAC system for a

particular wheel speed control range.

When the accelerator pedal is depressed the main throttle opens

resulting in generation of more torque. If the TRAC system identifies

excessive torque than required causing one or more wheels to spin, then it

applies brake to those wheels in small amount. This braking action is

intermittent till the wheel speed is reduced to the desired range for safe

cruising.

We can observe the highs and lows in the graph representing

increased wheel speed and TRAC wheel speed controlling action

respectively. Finally it comes to the required speed range and TRAC system

stops controlling action and goes back to monitoring state.

BENEFITS OF TRACTION CONTROL:

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Traction control systems bring overall improvement in the braking

system of the car. Here are a few of the benefits:

1. Traction control brake systems are helpful in avoiding accidents over

low-traction road surfaces.

2. The system assists in maintaining control over the car during sudden

twists and sharp turns on the road.

3. Slippage of the wheels during aggressive braking is prevented

avoiding accidents.

4. A reduction in stopping distances after the brakes are applied can help

in traffic.

5. TRAC system maintains directional control after breaking and reduces

skidding.

6. Traction control is beneficial when roads are wet and icy as it helps in

accelerate from a stop.

7. Traction control is helpful when you're driving a powerful car as it

regulates the power to the tires, keeping the car on the path you set.

8. Wheels cannot lock up suddenly as the grooving is avoided by ABS

system control.

9. In case of huge truck applications TRAC system can help in

accelerating as well as stopping efficiently.

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10. When accelerating, it gives you more traction because when you

accelerate, more weight shifts towards the rear.

11. By applying pressure to the slipping wheel, power is sent to the drive

wheel with the most gripping.

DISADVANTAGES:

Here are some reasons that car shoppers may be a little shy about getting into

a ride enhanced with traction control.

Cost of purchase. The high-functioning gear that's involved in

traction control can make a car an increasingly expensive purchase.

Those looking to save money on a vehicle may be looking for older

models that were cheaper to make.

Cost of maintenance. A vast range of things can damage traction

control or anti-lock brake sensors, and with each of these carrying a

hefty price tag, the cost of repairs can easily spin out of control. Those

with past experience paying for a damaged anti-lock brake system

may have a big aversion to getting even more in additional safety

features loaded into a vehicle.

Limited use. Traction control systems are not ideal for all kinds of

situations. Many experts claim drivers are better off with four wheel

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drive options for off-road use. Off-road use can also cause damages to

the traction control system.

APPLICATIONS:

There are many sectors in which Traction control system finds itself

useful. Here are few practical applications of TRAC System:

1. In road cars: Traction control has traditionally been a safety feature in

high-performance cars, which would otherwise need very sensitive

throttle input to keep them from spinning the driven wheels when

accelerating, especially in wet, icy or snowy conditions. In recent

years, traction control systems have become widely available in non-

performance cars, minivans, and light trucks.

2. In race cars: Traction control is used as a performance enhancement,

allowing maximum traction under acceleration without wheel spin.

When accelerating out of turn, it keeps the tires at the optimum slip

ratio.

3. In motorcycles: Traction control for a production motorcycle was first

available with the Honda ST1100 in 1992. By 2009, traction control

was an option for several models offered by BMW and Ducati, and the

model year 2010 Kawasaki Concours.

4. In off road vehicles: Traction control is used instead or in addition to

the mechanical limited slip differential. It is often implemented with

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an electronic limited slip differential as well as other computerized

control of the engine and transmission. Generally used in railway track

traction control systems.

5. Traction control is not just used for improving acceleration under

slippery conditions. It can also help a driver to corner more safely. If

too much throttle is applied during cornering, the drive wheels will

lose traction and slide sideways. This will be avoided by TRAC

system and helps the driver in cornering.

The 5 Safest Traction Control Cars

Although there are many vehicles that come with traction control, it's

important for you to know which traction control vehicles rank high in terms

of safety.

Chevy Malibu. This vehicle is available in four trims. It's given an

excellent rating for government safety and reliability tests and has a

four star rating for rollover incidents. Some of the safety features

offered for this model include tire-pressure monitoring, traction

control, airbags and an OnStar safety system

Buick LaCrosse. This vehicle has been given the highest score in

government crash tests. Traction control and stability are standard

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features on all trims. The vehicle also features a limited time

subscription to the OnStar safety system

Volvo C30. The Volvo C30 features a stability traction control

system, whiplash protection system and front and side airbags. Buyers

also have the option to add a blind spot information system or a rear

parking assist

Ford F-150. This vehicle can be programmed to limit its speed. It has

several safety features such as rollover resistance, electronic stability

control and side curtain airbags

Hyundai Genesis. The Hyundai Genesis features airbags, active front

head restraints, anti lock disc brakes and traction control. The vehicle

also does exceptionally well in government crash safety tests

Although price is often a determining factor when selecting a new

vehicle, it's equally important to choose a vehicle that safe. Vehicles

that are equipped with the latest safety features are also likely to have

lower insurance premiums.

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CONCLUSION:

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

between traction of different wheels evidencing apparent loss of road grip

that compromise steering control and stability of vehicles. Difference in slip

may occur due to turning of a vehicle or 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.

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REFERENCE:

1. “Mechanical Wear Fundamentals and Testing” – Dr. Raymond Bayer,

CRC Press.

2. “Theory of ground vehicles” - Prof. Jo Yung Wong, Carleton

University, Canada.

3. “Traction Control and other electronic trickery” – Prof. Andrew

Trevitt, California State University.

4. “How stuff works - TRAC System” - Davison technologies, U.S.A.

5. "Work-Related Roadway Crashes - Challenges and Opportunities for

Prevention" - Stephanie G. et al. The National Institute for

Occupational Safety and Health.

6. “AUTOSHOP 101” - Kevin Sullivan, Washington Post journalist.

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