ESP braking torque control circuit, function

Normal operation

This is the case when the driving state requires no control mode.

Antilock brake system (ABS) control mode

From the wheel speed signals the ESP control unit (N30/4) detects that the criteria for ABS control exist. The respective solenoid valves are actuated accordingly on an individual basis.

Acceleration slip regulation (ASR) control mode

As soon as a drive wheel tends to spin, the ESP control unit (N30/4) actuates the corresponding rear axle solenoid valves.

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Electronic Stability Program (Electronic-Stability-Program) (ESP) control mode

In the ESP control unit (N30/4) the signals of the wheel speeds, the steering angle, the yaw rate of the vehicle, the lateral acceleration as well as the brake pressures are detected and processed by a drive status regulator. After the evaluation of input signals, the required solenoid valves are actuated in order to regulate the brake pressure in the individual wheel brakes.

Brake Assist (BAS) operation

From the pressure buildup speed, the ESP control unit (N30/4) detects that an emergency stop situation exists and initiates
BAS mode.

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Electronic brake force distribution (EBV) operation

EBV determines the maximum permissible brake pressure for both rear wheel brakes based on the rpm difference between the front and rear axle wheels. Based on the vehicle load, EBV regulates the brake pressure at the rear axle so that overbraking is prevented.

EBV replaces the original pressure/load-dependent rear axle regulator which distributed the brake force between the axles as per predetermined, fixed characteristics.

Control mode with ESP deactivated

ESP drive torque control is switched off up to a speed of 60 km/h by actuating the "ASR OFF" switch (N72/1s5) in the upper control panel control unit (N72/1).