4- and 6-channel anti-lock braking systems (ABS) have been increasingly used in European trucks and buses since 1901. In a second generation of the WABCO-ABS the control of wheel slip caused by service brake or retarder is extended to operation control drive slip (ASR). For this, most components of the ABS are also applied. The higher integrated electronic control unit contains correspondingly extended software functions but less components than the first generation. A few additional valves and actuators are necessary to actuate a brake if only one driven wheel starts spinning or to reduce the engine power if all driven wheels develop unacceptable drive slip.
This paper describes structural and functional principles of this control system for power-braked buses, trucks and tractors.