Overview
This document contains information on:
General
Function requirements
Function
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 transmitted to the relevant wheel. The resulting forces stabilize the vehicle.