A Study on Optimal Yaw Moment Distribution Control Based on Tire Model

Vehicle stability control system can enhance the vehicle stability and handling in emergency situation through the control of traction and braking forces at the individual wheels. In order to achieve the desired performance, we must exactly calculate compensated yaw moment, and control the wheel slip rate to generate braking force. However, the yaw moment is highly dependent on the status of tire dynamics at each wheel. In this study, we propose optimal yaw moment distribution controller based on tire model according to the normal forces, the road condition, the slip rate and the slip angle to cope with nonlinear tire dynamics. The proposed controller for distributing the desired tire slip rate makes used of the optimization technique based on the tire nonlinear model. It minimizes the braking control force corresponding to the desired tire slip at each wheel. Especially, the proposed optimal controller can make the maximum yaw moment of vehicle using an extra wheel when the main controlled wheel can’t make more longitudinal / lateral force in unstable slip rate range. We verify the basis and the effect of this optimal moment distribution method through vehicle tests.