GF42.31-P-0001SL Brake Assist (BAS) Function

GF42.31-P-0001SL Brake Assist (BAS) function





Braking behavior
Studies when driving normally on the driving simulator and on the test track have shown that most drivers in emergency braking situations, above all in the initial phase of brake application, in fact press the brake pedal quickly but not hard enough.

A distinction is made between:
^ Hesistant 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 brake pedal is depressed.

If this is the case, the high-pressure charging pump ([]ml) in the traction system hydraulic unit A7/3(A7/3) is activated and consequently the full braking 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, SPS [PML] and BAS control unit (N47-5). The pressure reservoir in the traction systems hydraulic unit is used for pressure generation (A7/3).

After the engine is started, 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.

A7/3 Using the rate of pressure increase in the front axle prepressure sensor and the signal from the pedal value sensor the ESP and BAS control unit B37/1 (N47-5) calculates the operating speed of the brake pedal. The operating speed of the brake pedal and vehicle speed is detected in the ESP, SPS [PML] and BAS control unit (N47-5).

A7/3 If the pedal speed is greater than the threshold value specified for the particular vehicle speed, the high-pressure charging pump in the traction system hydraulic unit is activated and full braking power is achieved. A7/3

BAS is not used in the event of a defect; this is displayed by the left multifunction display (A1p13) and right multifunction display (A1p15) in the instrument cluster (A1). The normal function of the brake is not affected by this.