TRACTION CONTROL SYSTEMS
TABLE OF CONTENTS:
Sl.No. Title Page No.
1. Abstract 02
2. Introduction 03
3. History 04
4. Literature survey 05
5. Block diagram of traction control system (TRAC) 05
6. Working of traction control system 06
7. Case studies 07
8. Scope 08
9. Summary of review 09
10. TRAC system components of Toyota supra mark IV 10
11. TRAC wheel speed control 12
12. Benefits of traction control 13
13. Applications 14
14. Reference 15
P.E.S. College of Engineering 1
TRACTION CONTROL SYSTEMS
A TOPIC SEMINAR ON
“TRACTION CONTROL SYSTEMS”By,
Vijay S
(USN – 4PS07ME093)
Department of Mechanical Engg,
P.E.S.C.E. Mandya.
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.
INTRODUCTION:
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TRACTION CONTROL SYSTEMS
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.
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:
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TRACTION CONTROL SYSTEMS
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 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.
LITERATURE SURVEY:
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TRACTION CONTROL SYSTEMS
BLOCK DIAGRAM OF TRACTION CONTROL SYSTEM (TRAC):
Fig 1
WORKING OF TRACTION CONTROL SYSTEM:
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TRACTION CONTROL SYSTEMS
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 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.
CASE STUDIES:
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TRACTION CONTROL SYSTEMS
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.
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:
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TRACTION CONTROL SYSTEMS
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.
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.
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TRACTION CONTROL SYSTEMS
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.
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.
SUMMERY 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.
TRAC SYSTEM COMPONENTS OF TOYOTA SUPRA MARK IV:
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TRACTION CONTROL SYSTEMS
Fig 2
The Toyota Supra is a sports car that was produced by Toyota Motor Company
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TRACTION CONTROL SYSTEMS
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 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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TRACTION CONTROL SYSTEMS
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
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.
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.
APPLICATIONS:
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TRACTION CONTROL SYSTEMS
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 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.
REFERENCE:
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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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