Brake Force Distribution, Basic Function - GF42.47-P-1004A

Model All (4xWD, CAR) 

Overview 

This document contains information on:

• General 
• Function requirements 
• Function 
  • Detecting driving situation 
  • Building up or depleting brake force 

General 

When the driver brakes, a larger proportion of the vehicle weight is shifted to the front wheels. As a result of this weight transfer, the rear wheels are relieved and lock earlier than the front wheels.

In order to prevent the rear wheels from locking, a part of the brake force is transferred from the rear wheels to the front wheels.

Function requirements 

• Drive train operational
• Engine in operation
• Brake and traction system functional

Function 

Detecting driving situation 

In order to calculate potential interventions, the function records the following information:

• Yaw velocity
• Lateral forces on the wheels
• Longitudinal forces on the wheels

The side-slip angle (angle between vehicle longitudinal axis and direction of movement of the vehicle's center of gravity) is determined using the yaw rate (speed of vehicle rotation about vertical axis).

The lateral forces on the wheels are determined using the following information:

• Yaw velocity
• Lateral acceleration
• Steer angle of the front wheels

The longitudinal forces on the wheels are determined using the following information:

• Engine torque
• Transmission stage
• Brake pressure on each wheel

Building up or depleting brake force 

The function prevents overbraking of the rear axle. In addition, it improves vehicle stability when braking on bends by, if necessary, reducing the brake pressure on the rear wheel on the inside of the curve or increasing the brake pressure on the front wheel on the outside of the curve.

If the measured yaw velocity does not match the specified value or if the determined side-slip angle is too large, a signal to build up or reduce brake force is sent to the relevant wheel. The resulting forces stabilize the vehicle.

	Additional basic functions
	Electromechanical brake booster, basic function	Vehicles with automatic operation of service brake function	GF42.31-P-2003A
	Brake booster, basic function		GF42.31-P-2004A
	Electronic Stability Program control unit, basic function		GF42.45-P-9890A
	Traction system hydraulic unit, basic function		GF42.50-P-2000A