ESP Control Function ABS

Braking Process In Normal Mode





Legend
b Brake pressure


ABS Pressure Build-up Control Mode
Every ABS control starts with a normal braking process which the driver performs via the brake pedal.

The ESP control module recognizes the braking process via the stop lamp switch and decelerated wheel speeds.

The brake pressure is built-up via the charging piston unit (14), the two switchover solenoid valves (y18 and y19) and the solenoid valves (y6. y8, y10 and y 12).

This pressure build-up phase can take place individually at each wheel during the ADS control process.

The pressure is reduced via the same solenoid valves during a normal braking process.

ABS Control Mode - Pressure Holding





(The control process or valve positions shown in the example relate to the FR and RL brakes).

If a wheel tends to lock during the braking process. ABS prevents a further pressure build-up. The ESP control module introduces the pressure-holding phase from the slip values of the wheels (FR and RL). The pressure-holding phase is achieved by actuating (closing) the pressure-holding solenoid valves (y8 and y10).
The pressure-reduction solenoid valves (y9 and y11) remain closed in this control phase.

ABS Control Made - Pressure Reduction





(The control process or valve positions shown in the example relate to the FR and RL brakes).

The ESP control module introduces the pressure-reduction phase from the slip values of the wheels (FR and RL). The pressure-reduction phase is achieved by actuating (opening) the pressure-reduction solenoid valves (y9 and y11).The pressure holding solenoid valves (y8 and y10) remain actuated (closed) in this control phase.

During the pressure-reduction phase brake fluid flows into the hiqh-pressure/return pumps (p1 and p2) via the accumulator (11) The high-pressure/return pumps deliver the brake fluid from the brake calipers back into the brake circuits against the existing pressure.