1987-11-01

Traction Control (ASR) for Commercial Vehicles. A Further Step Towards Safety on our Roads 872272

Alongside steering, accelerating and braking are the basic operations in the automobile which are nowadays still left to the driver to perform in their entirety. In performing these basic functions, it may come about that excessive demands are made upon a driver, these arising due to poor road conditions - rain, snow and ice - or as a result of suddenly changing traffic situations.
With the introduction of anti-lock braking systems (ABS), a decisive step has been taken to increase active driving and traffic safety. The ABS prevents the lockup of the wheels during overbraking. The vehicle remains steerable and retains stable directional control. Furthermore, in many cases, a shorter braking distance is gained compared to braking with the wheels locked up.
BOSCH has been manufacturing and supplying ABS for passenger cars since 1978 and for commercial vehicles and buses since 1981. ABS has proved to be an overwhelming success in practical usage. The anti-look braking system has now been complemented by electronic traction control or automatic spin regulation (ASR). ASR prevents the driving wheels from spinning when over-accelerating on slick and slippery roadways. The wheel slip is automatically controlled within an optimum range by the intervention of the brake as well as by the reduction of engine torque. On the one hand, the result is that the propulsive force is increased in comparison to the spinning driving wheels, and on the other hand, the stability of the vehicle is not lost when accelerating.
In this way. ASR prevents the negative effects caused by the driver over-accelerating. Driving-off and accelerating are thus achieved in a perfect manner.
A great advantage of ASR is the low degree of wear on the tires as well as on the complete drive train.
For example, if the right-hand side of a city-bus pull-in is iced over and on the left-hand side the concrete surface is dry, mechanical differentials are frequently damaged on driving across the icy surface.
If the vehicle is equipped with ASR, the required locking effect between the driving wheels is developed. This is done by sensitively braking the spinning wheel and thus balancing the wheel speeds of the driving wheels (braking-force regulator).
If, however, the left-hand side of the pull-in is iced over in addition to the right-hand side, both driving wheels spin at the same time when acceleration is too heavy. In this case. ASR does not intervene via the brakes, but via an automatic reduction of the engine torque. For example, the control unit of the electronic engine-power control function is informed of the necessary reduction in torque and it sees to the performance of this reduction (engine-speed governor).
If the braking-force regulator or the engine speed governor becomes active, the ASR indicator lamp lights up on the instrument panel. In this way, the driver is informed of the slippery condition of the road surface and is able to immediately adapt his manner of driving accordingly (slippery-condition warner).

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