Anti-Lock Control - Traction Control and Stability Assist

The anti-lock brake system (ABS) with traction control and stability assist consists of the following components:

• hydraulic control unit (HCU)
• brake booster and master cylinder
• rear wheel speed sensors
• front wheel speed sensors
• yaw rate sensor (integral to sensor cluster)
• accelerometer (integral to sensor cluster)
• steering wheel rotation sensor

The stability assist recognizes critical driving conditions, such as panic reactions in dangerous situations and stabilizes the vehicle by individually braking each wheel and using engine control intervention without the need to actuate the brake or the accelerator pedal.

The stability assist adds a further function known as Electronic Stability Program (ESP) to the anti-lock brake system (ABS) and traction control system (TCS). Where as the ABS/TCS function controls wheel slip during braking and acceleration (longitudinal dynamics), the active yaw control stabilizes the vehicle about its vertical axis.

Sensors measure the position of the steering wheel, the pressure in the brake master cylinder, the yaw velocity (yaw rate) and the acceleration transverse to the vehicle (lateral acceleration). This makes it possible to compare the driver's intention with the momentary vehicle behavior so that in the event of the vehicle becoming unstable, the stability assist system can initiate the appropriate corrective action.