Braking Assistant (BAS) - Operation - GF42.31-P-0001T

MODEL 211 up to 31.5.06 

except CODE (494) USA version 

except CODE (498) Japan version 

MODEL 211 up to 30.6.06 

with CODE (494) USA version 

with CODE (498) Japan version 

Brake diagram 

Fig 1: Braking Behavior Graph

Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Braking behavior 

A distinction is made between:

• Hesitant braking, e.g. in the initial phase the driver applies too little pedal force and increases it too slowly.
• Inadequate braking, e.g. the driver applies too little pedal force throughout the entire braking application.

Brake Assist (BAS) has been developed to improve these situations.

Task 

Brake Assist (BAS) is part of the active safety system. It becomes active when the driver brakes very quickly in an emergency situation. The system detects whether an emergency braking situation exists on the basis of the speed at which the driver presses the brake pedal. If this is the case, the high-pressure charging pump (A7/3m1) in the traction system hydraulic unit (A7/3) must be activated and as a result the full brake force is reached. If the driver releases the brake, this is detected and the high-pressure charging pump (A7/3m1) is switched off again.

Advantages:

• The BAS system reduces the accident risk in dangerous situations by optimum braking deceleration and thus assists the driver considerably.
• The BAS system significantly reduces the brake distance during hesitant or inadequate braking.

Function overview 

Brake Assist (BAS) is fully integrated in the Electronic Stability Program (ESP). The electronics are located in the ESP control unit (N47-5). The pressure reservoir in the traction systems hydraulic unit is used for pressure generation (A7/3).

After the driver starts the engine, a vehicle identification and self-check of the system takes place.

BAS is operational when no fault exists and the vehicle exceeds a speed of 10 km/h after starting off. BAS can be activated down to a speed of 3 km/h.

Using the speed of the pressure rise in the front axle pre-pressure sensor (A7/3b1) and the signal from the SBC pedal value sensor (B37/1) the ESP control unit (N47-5) calculates the operating speed of the brake pedal. The operating speed of the brake pedal and the vehicle speed are recorded in the ESP control unit (N47-5).

If the pedal speed is greater than the threshold value specified for the respective vehicle speed, the high-pressure charging pump (A7/3m1) in the traction system hydraulic unit (A7/3) is actuated and thus the full brake force is reached.

The is not used in the event of a defect; this is displayed by the multifunction display (A1p13) in the instrument cluster (A1). The normal function of the brake is not affected by this.