ASR V/ETS Control Functions ABS

Braking Process In Normal Mode
ABS Control Mode Pressure Build-Up





Each ABS control starts with a normal braking process, which the driver carries out via the brake pedal.
The ASR V/ETS control module recognizes the braking process via the stop lamp switch and the reduced wheel speeds.

The brake pressure at the front axle is built up via the solenoid valves (y6 and y8). The brake pressure at the rear axle is built up via the switchover solenoid valve (y5) and the solenoid valves (y1O and y12).
During a normal braking process, pressure is built up via the same solenoid valves.

ABS Control Mode - Pressure Holding





If a wheel tends to lock during a braking process, ABS prevents a further pressure build-up. From the slip values of the braked wheels, the ASR V/ETS control module introduces the pressure holding phase.

The pressure holding phase is introduced by actuating the solenoid valves (y6, y8, y1O and y12). All solenoid valves (y6 to y13) are closed in this control phase; the pressure at the brake calipers therefore remains constant.

ABS Control Mode - Pressure Reduction





The ASR V/ETS control module introduces the pressure reduction phase from the slip values of the braked wheels. The pressure reduction phase is introduced by actuating (opening) the solenoid valves (y7, y9, y11 and y13), The solenoid valves (y6, y8, y1O and y12) remain actuated (closed) in this control phase.
During the pressure reduction phase brake fluid flows back into the high-pressure pump/return pump (p1 and p2) via the accumulator (11). From there the high-pressure pump/return pump in the two brake circuits delivers the brake fluid back into the master brake cylinder against the existing pressure. This takes place in the rear axle brake circuit via the switchover solenoid valve (y5). A silencer (10) is fitted to each brake circuit to damp the delivery noise.