Active Front Steering for Driver's Steering Comfort and Vehicle Driving Stability

In this paper, an active front steering (AFS) controller with a new variable steering ratio (VSR) map is proposed to enhance the vehicle stability and consider the driver's steering comfort. The properties of the steering sensitivity and the yaw rate gain are investigated and utilized to construct a 3D VSR map in terms of the steering wheel angle and the longitudinal vehicle velocity. Based on this 3D VSR map, the AFS controller is designed by adopting the model predictive control (MPC) approach. An optimum solution of the MPC controller is determined by taking into account the AFS actuator limits. The proposed algorithm is validated in simulations by using the commercial software, CarSim and MATLAB/Simulink.