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The principle of operation of the traction control system

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The principle of operation of the traction control system
The principle of operation of the traction control system

Today, in the world of cars, there are many electronic systems and assistants that work to increase active and passive safety. Thus, electronics can prevent accidents that occur when the car is moving. Now all vehicles are required to be equipped with a system such as ABS. But it's far from the only system on the base list. So, models of a class above are regularly equipped with ASR. What it is? This is an anti-slip system. We will consider its principle of operation and advantages further.


So what is ASR? This is an element of the active safety of the car. The action of ASR is aimed at keeping the vehicle's wheels in contact with the road while driving.

asr traction control system

In the common people, this system is called "antibuks". Officialname - automatic slip control system. Thus, the work of the traction control system is aimed at protecting the driving pair of wheels from slipping on a wet or icy surface, as well as during a sharp start from a standstill or during other dangerous maneuvers.

About the abbreviation

It should be noted that ASR is not the only abbreviation used for this system. So, on Volvo cars, it is marked as STC, on Toyota - TRC (Traction Control), on Opel - DSA, on Range Rovers - ETC. However, in most cases, this system can be recognized by the first marking. Remarkably, it works the same on all cars. Therefore, it cannot be said that ASR on Volkswagen is worse than on Audi and Mercedes, and vice versa. On any vehicle, it performs the function of maintaining the dynamic course of the car and works closely with the anti-lock wheel system.

Operation principle

ASR always works, regardless of the current vehicle speed. However, its functionality is slightly different:

  • At speeds from 0 to 80 kilometers per hour, the system transmits torque by braking the vehicle's drive wheels.
  • At speeds over 80 kilometers per hour, efforts are regulated by reducing the torque that is transmitted from the engine.
operation of the traction control system

An anti-slip system operates based on signals from different sensors:

  • ABS.
  • Frequencies of rotationwheels.

As a result, the control unit determines the following characteristics:

  • Vehicle speed. The data is based on the angular speed of the wheels on the non-driven axle.
  • Angular acceleration of drive wheels.
  • The type of movement of the machine. Distinguish between curvilinear and rectilinear movement of the car.
  • The amount of slippage of the driving wheels. The information is obtained based on the difference in the angular speed of the wheels on the driving and driven axles.

Depending on the received data, the electronics control the brake pressure or act on the engine itself, reducing its torque.

In the first case, the brake pressure control is cyclic. So, there are several phases in the cycle:

  • Increase.
  • Hold.
  • Pressure release.

The increase in hydraulic fluid pressure contributes to the braking of the drive wheels. This is due to the inclusion of the return pump. This opens the high pressure valve and closes the changeover valve. This pressure is maintained by the return pump. A reset is performed after slipping. In this case, the intake and switching valves are activated. This cycle may repeat several times, depending on the current traffic situation.

how to disable traction control

But torque control is somewhat different. This process is carried out when the internal combustion engine control system is activated. Based on the signals received fromsensors of the angular speed of the wheels and the actual torque (which is measured by the ECU), the ASR control unit calculates how much the power of the power unit needs to be reduced. This information is transmitted to the electronic engine control unit. But how is this data realized? The reduction of power and torque by the ASR system occurs in several ways:

  • When changing the position of the throttle (it closes more than it should be).
  • Missing fuel injection in the system.
  • Misfiring ignition pulses.
  • When canceling a gear change. But this is only possible with an automatic transmission.
  • When changing the ignition timing.
  • disable traction control

How does the driver know that the ASR system has taken effect?

The driver will be informed about this by a special control lamp on the instrument panel. At the end of the system and when the car comes out of slippage, this lamp disappears. The engine and braking system are working as usual.

Benefits of using

This system is installed on cars for a reason. She really benefits. The main advantage of having ASR is an increase in traffic safety. The driver is not immune from mistakes. However, electronics are able to correct them and prevent the car from skidding, which can lead to an accident. Also, the ASR traction control system allows you to extend the life of the engine, since the torque is distributed moresmoothly. Another advantage of this system is less tire abrasion that could occur in the event of unauthorized slip. In addition, ASR has a positive effect on fuel consumption, albeit slightly.

How to turn off the traction control?

If desired, any driver can forcibly disable ASR. To do this, the machine has a special button.

operation of the traction control system

After turning off the traction control system, the car will enter turns with the sliding of the drive axle. In this case, in the event of braking, the ABS system will still work. Also, the corresponding lamp on the instrument panel will light up. It is a yellow flashing triangle with an exclamation point. It lights up when the wheels spin. And it doesn't matter what the current speed is - 5 or 100 kilometers per hour.

system operation

In what cases is it recommended to forcibly turn off the traction control system? This must be done in winter when it is impossible to start on snow or on an icy surface. After leaving a difficult area, the manufacturer recommends reactivating the ASR traction control system. The yellow indicator on the panel will turn off.


So, we found out how the traction control system works and why it is needed. As you can see, ASR is designed to increase the safety of the car in difficult conditions, eliminating the possibility of slipping and skidding of the vehicle. However, no matter how smart the system is, 100 percent protectionshe doesn't give. Therefore, you should always rely only on your driving skills and speed of reaction.

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