System for controlling yaw moment based on an estimated coefficient of friction

Yaw moment control apparatus for improving the driving behavior of an automotive vehicle tending to oversteering or understeering, the vehicle having an engine and front and rear axles, each axle having a plurality of wheels, each wheel having a brake, the vehicle including means for determining a vehicle reference velocity from the rotational velocities of the wheels, said apparatus comprising:

• a plurality of sensors for generating signals representing a vehicle steering angle, a lateral acceleration of the vehicle, and a measured yaw rate of the vehicle;
• yaw rate change estimating means for generating a yaw rate change value representing a change in vehicle yaw rate based on the vehicle steering angle, the vehicle reference velocity and the measured yaw rate;
• means for generating a value representing a velocity of the side slip angle based on the vehicle reference velocity, the lateral acceleration and the measured yaw rate;
• yaw control law means for generating a value representing an engine torque adjustment based on the yaw rate change value and the velocity of the side slip angle, said engine torque adjustment value being applied to control the yaw rate of the vehicle;
• and
• means for determining a coefficient of friction based on the vehicle reference velocity, the lateral acceleration, the measured yaw rate and the steering angle, wherein said coefficient of friction is used by the yaw control law means for determining the engine torque adjustment value.

A device for controlling the yawing moment of a four-wheel motor vehicle during travel in a curve, comprising:

• yaw control means for generating a value representing a desired yaw rate adjustment that is to be applied to said vehicle,
• means for recognizing the current coefficient of friction, and for providing a value representing the current coefficient of friction to the yaw control means for use in determining said desired yaw rate adjustment;
• means for determining whether the vehicle is traveling through a curve
• means for enabling said current coefficient of friction recognizing means only while the vehicle is traveling through a curve.