BAS brake application, function

GF42.31-S-2000C

BAS brake application, function

19.5.14

MODEL

415

Overview

Studies have shown that most drivers in emergency driving situations, above all in the initial phase of brake application, do depress the brake pedal quickly but not hard enough. A distinction is made between:

 A hesitant brake application, e.g. the driver applies too little pedal force in the initial phase and increases it too slowly.

 Inadequate braking, e.g. the driver applies too little pedal force throughout the entire brake application.

The Brake Assist System (BAS) has been developed to improve this situation. The BAS is integrated in the Electronic Stability Program (ESP) control unit (N30/4) and operates without additional sensors.

The ESP® control unit reads in the signals from the following system components and evaluates them:

 Left front axle rpm sensor (L6/1).

 Right front axle rpm sensor (L6/2).

 Left rear axle rpm sensor (L6/3).

 Right rear axle rpm sensor (L6/4).

 Brake pressure sensor integrated in the ESP® control unit.

 Vehicle speed from the radio (A2).

 CDI control unit (N3/9) or ME-SFI control unit (N3/10).

 Brake lights switch (S9/1).

 ESP® OFF button (S76/6).

Activation of BAS

Using the read-in information, the ESP® control unit checks whether all of the following conditions for activating the BAS are fulfilled, and then activates the BAS:

 After the engine is started and if no fault is present following the self-diagnosis, the BAS is released.

 Minimum vehicle speed of 6 to 10 km/h is reached.

 Brake lights switch is activated.

 When the brake pedal is depressed, the pedal speed is greater than the specified limit value for the associated vehicle speed.

Function - brake application with BAS

Brake application with the BAS functions in the same way as a normal brake application, only the pressure is built up more quickly corresponding to the pedal speed. The ESP® control unit uses the brake pedal actuation speed and the vehicle speed to detect whether the preconditions exist for activation of the BAS.

Deactivation of BAS

Using the read-in information, the ESP® control unit checks whether at least one of the following conditions for deactivating the BAS is fulfilled, and then deactivates the BAS:

 Vehicle speed = 0 km/h.

 The engine is switched off.

 Maximum ON time of the BAS has been exceeded.

 No signal from the brake lights switch.

 Malfunction of the BAS.

 Brake pedal pressure is reduced by the driver to such an extent that emergency braking is no longer required.

 Reverse travel.

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