Traction control system
Encyclopedia
A traction control system (TCS), also known as anti-slip regulation (ASR), is typically (but not necessarily) a secondary function of the anti-lock braking system
(ABS) on production motor vehicle
s, designed to prevent loss of traction
of driven road wheels. When invoked it therefore enhances driver control as throttle input applied is mis-matched to road surface conditions (due to varying factors) being unable to manage applied torque
.
Intervention consists of one or more of the following:
Typically, traction control systems share the electro-hydraulic brake actuator (but does not use the conventional master cylinder and servo), and wheel speed sensors with the anti-lock braking system
.
. 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 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. 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.
Active-differential, in turn, is controlled by an assembly of electromechanical sensors collaborating with a traction control unit.
module) detects one or more driven wheels spinning significantly faster than another, it invokes ABS ecu to apply brake friction to wheels spinning with lessened traction. Braking action on slipping wheel(s) will cause power transfer to wheel axle(s) with traction due to the mechanical action within a differential. All-wheel drive AWD
vehicles often have an electronically controlled coupling system in the transfer case
or transaxle
engaged (active part-time AWD), or locked-up tighter (in a true full-time set up driving all wheels with some power all the time) to supply non-slipping wheels with (more) torque.
This often occurs in conjunction with the powertrain computer reducing available engine torque by electronically limiting throttle application and/or fuel delivery, retarding ignition spark, completely shutting down engine cylinders, and a number of other methods, depending on the vehicle and how much technology is used to control the engine and transmission.
, an effort to ban TC has led to the change of rules for 2008: every car must have a standard (but custom mappable) ECU, issued by FIA, which is relatively basic and does not have TC capabilities. NASCAR suspended a Whelen Modified Tour
driver, crew chief, and car owner for one race and disqualified the team after crossing the finish line first in a September 20, 2008 race at Martinsville Speedway
after finding questionable wiring in the ignition system, which can often be used to implement traction control.
in front wheel drive vehicles and oversteer in rear wheel drive vehicles. Traction control can prevent this from happening by limiting power to the wheels. It cannot increase the limits of grip available and is used only to decrease the effect of driver error or compensate for a driver's inability to react quickly enough to wheel slip.
Automobile manufacturers state in vehicle manuals that traction control systems should not encourage dangerous driving or encourage driving in conditions beyond the drivers' control.
Anti-lock braking system
An anti-lock braking system is a safety system that allows the wheels on a motor vehicle to continue interacting tractively with the road surface as directed by driver steering inputs while braking, preventing the wheels from locking up and therefore avoiding skidding.An ABS generally offers...
(ABS) on production motor vehicle
Motor vehicle
A motor vehicle or road vehicle is a self-propelled wheeled vehicle that does not operate on rails, such as trains or trolleys. The vehicle propulsion is provided by an engine or motor, usually by an internal combustion engine, or an electric motor, or some combination of the two, such as hybrid...
s, designed to prevent loss of traction
Traction (engineering)
Traction refers to the maximum frictional force that can be produced between surfaces without slipping.The units of traction are those of force, or if expressed as a coefficient of traction a ratio.-Traction:...
of driven road wheels. When invoked it therefore enhances driver control as throttle input applied is mis-matched to road surface conditions (due to varying factors) being unable to manage applied torque
Torque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....
.
Intervention consists of one or more of the following:
- Reduces or suppress spark sequence to one or more cylinderCylinder (engine)A cylinder is the central working part of a reciprocating engine or pump, the space in which a piston travels. Multiple cylinders are commonly arranged side by side in a bank, or engine block, which is typically cast from aluminum or cast iron before receiving precision machine work...
s - Reduce fuel supply to one or more cylinders
- Brake force applied at one or more wheels
- Close the throttle, if the vehicle is fitted with drive by wireDrive by wireDrive-by-wire, DbW, by-wire, or x-by-wire technology in the automotive industry replaces the traditional mechanical control systems with electronic control systems using electromechanical actuators and human-machine interfaces such as pedal and steering feel emulators...
throttle - In turbo-charged vehicles, a boost control solenoid can be actuated to reduce boost and therefore engine power.
Typically, traction control systems share the electro-hydraulic brake actuator (but does not use the conventional master cylinder and servo), and wheel speed sensors with the anti-lock braking system
Anti-lock braking system
An anti-lock braking system is a safety system that allows the wheels on a motor vehicle to continue interacting tractively with the road surface as directed by driver steering inputs while braking, preventing the wheels from locking up and therefore avoiding skidding.An ABS generally offers...
.
History
The predecessor of modern electronic traction control systems can be found in high-torque, high-power rear-wheel drive cars as a limited slip differentialLimited slip differential
A limited slip differential is a type of differential gear arrangement that allows for some difference in angular velocity of the output shafts, but imposes a mechanical bound on the disparity...
. 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
Buick
Buick is a premium brand of General Motors . Buick models are sold in the United States, Canada, Mexico, China, Taiwan, and Israel, with China being its largest market. Buick holds the distinction as the oldest active American make...
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. 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.
Overview
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.
Operation
When the traction control computer (often incorporated into another control unit, like the anti-lock braking systemABS
- Anatomy :* Abdominal muscles , which is the rectus abdominis or the stomach muscles-Music and media:Music ensembles* A.B.'s, a Japanese 80's instrumental band* Abingdon Boys School, a Japanese rock band...
module) detects one or more driven wheels spinning significantly faster than another, it invokes ABS ecu to apply brake friction to wheels spinning with lessened traction. Braking action on slipping wheel(s) will cause power transfer to wheel axle(s) with traction due to the mechanical action within a differential. All-wheel drive AWD
AWD
AWD may refer to:* AWD Holding, , a German company* Acute Watery Diarrhoea, a symptom associated with cholera* Afghan War Diary, a collection of thousands of US military documents that were leaked to the public via Wikileaks in July, 2010* Agency Worker Directive * Air Warfare Destroyer* All-wheel...
vehicles often have an electronically controlled coupling system in the transfer case
Transfer case
A transfer case is a part of a four-wheel-drive system found in four-wheel-drive and all-wheel-drive vehicles. The transfer case is connected to the transmission and also to the front and rear axles by means of drive shafts...
or transaxle
Transaxle
In the automotive field, a transaxle is a major mechanical component that combines the functionality of the transmission, the differential, and associated components of the driven axle into one integrated assembly....
engaged (active part-time AWD), or locked-up tighter (in a true full-time set up driving all wheels with some power all the time) to supply non-slipping wheels with (more) torque.
This often occurs in conjunction with the powertrain computer reducing available engine torque by electronically limiting throttle application and/or fuel delivery, retarding ignition spark, completely shutting down engine cylinders, and a number of other methods, depending on the vehicle and how much technology is used to control the engine and transmission.
Use of traction control
- In road cars: Traction control has traditionally been a safety feature in premium high-performance cars, which otherwise need sensitive throttle input preventing spinning 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.
- In race carsAuto racingAuto racing is a motorsport involving the racing of cars for competition. It is one of the world's most watched televised sports.-The beginning of racing:...
: 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 optimal slip ratioSlip ratioSlip ratio is a means of calculating and expressing the locking status of a wheel and is vital to the effectiveness of any anti-lock braking system....
. - In motorcycleMotorcycleA motorcycle is a single-track, two-wheeled motor vehicle. Motorcycles vary considerably depending on the task for which they are designed, such as long distance travel, navigating congested urban traffic, cruising, sport and racing, or off-road conditions.Motorcycles are one of the most...
s: Traction control for a production motorcycle was first available with the Honda ST1100Honda ST1100The Honda ST1100, also known as the Pan-European, is a sport touring motorcycle that was manufactured by Honda until 2002.- History :The ST1100 began its production in 1990 and ended in 2002, although the police variant, the ST1100P, was available for several more years.A revamped model, the...
in 1992. By 2009, traction control was an option for several models offered by BMWBMW MotorradBMW Motorrad is the motorcycle brand of the German company BMW, part of its Corporate and Brand Development division. The current General Director of the unit is Hendrik von Kuenheim....
and Ducati, and the model year 2010 Kawasaki Concours 14Kawasaki 1400GTRThe Kawasaki 1400GTR, also known as the Concours 14 or ZG1400 in some markets, is a motorcycle produced by Kawasaki. The 1400GTR was introduced in September 2007 and is based on the ZX-14 platform....
(1400GTR). - In off roadOff RoadOff Road may refer to:*Super Off Road, 1989 arcade game released by Leland Corporation*Off Road Challenge, 1998 console game released by Nintendo*Ford Racing: Off Road, 2008 video game published by Empire Interactive...
vehicles: Traction control is used instead or in addition to the mechanical limited slip or locking differentialLocking differentialA locking differential, diff-lock or locker is a variation on the standard automotive differential. A locking differential may provide increased traction compared to a standard, or "open" differential by restricting each of the two wheels on an axle to the same rotational speed without regard to...
. It is often implemented with an electronic limited slip differential, as well as other computerized controls of the engine and transmission. The spinning wheel is slowed down with short applications of brakes, diverting more torque to the non-spinning wheel; this is the system adopted by Range Rover models in the mid 1990's, for example. This form of traction control has an advantage over a locking differential, as steering and control of a vehicle is easier, so the system can be continuously enabled. It creates less stress on drive-trains, particularly important to vehicles with an independent suspensionIndependent suspensionIndependent suspension is a broad term for any automobile suspension system that allows each wheel on the same axle to move vertically independently of each other. This is contrasted with a beam axle, live axle or deDion axle system in which the wheels are linked – movement on one side affects...
, generally weaker compared to solid axlesBeam axleA beam axle is a suspension system, also called a solid axle, in which one set of wheels is connected laterally by a single beam or shaft...
. On the other hand, only half of the available torque will be applied to a wheel with traction, compared to a locked differential, and handling is less predictable.
Controversy in motorsports
Very effective yet small units are available that allow the driver to remove the traction control system after an event if desired. In Formula OneFormula One
Formula One, also known as Formula 1 or F1 and referred to officially as the FIA Formula One World Championship, is the highest class of single seater auto racing sanctioned by the Fédération Internationale de l'Automobile . The "formula" designation in the name refers to a set of rules with which...
, an effort to ban TC has led to the change of rules for 2008: every car must have a standard (but custom mappable) ECU, issued by FIA, which is relatively basic and does not have TC capabilities. NASCAR suspended a Whelen Modified Tour
Whelen Modified Tour
The NASCAR Whelen Modified Tour is a stock car racing series owned and operated by NASCAR in the Modified division. The Modified division is NASCAR's oldest division, and its one of two open-wheeled divisions...
driver, crew chief, and car owner for one race and disqualified the team after crossing the finish line first in a September 20, 2008 race at Martinsville Speedway
Martinsville Speedway
Martinsville Speedway is an International Speedway Corporation-owned NASCAR stock car racing track located in Henry County, near Ridgeway, Virginia, just to the south of Martinsville. At in length, it is the shortest track in the NASCAR Sprint Cup Series. The track was also one of the first paved...
after finding questionable wiring in the ignition system, which can often be used to implement traction control.
Traction control in cornering
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 occurs as understeerUndersteer
Understeer and oversteer are vehicle dynamics terms used to describe the sensitivity of a vehicle to steering. Simply put, oversteer is what occurs when a car turns by more than the amount commanded by the driver...
in front wheel drive vehicles and oversteer in rear wheel drive vehicles. Traction control can prevent this from happening by limiting power to the wheels. It cannot increase the limits of grip available and is used only to decrease the effect of driver error or compensate for a driver's inability to react quickly enough to wheel slip.
Automobile manufacturers state in vehicle manuals that traction control systems should not encourage dangerous driving or encourage driving in conditions beyond the drivers' control.