Driver assisted fuzzy control of yaw dynamics for 4WD vehicles

A new model for Four Wheel Driving (4WD) vehicles and a fuzzy control system that enhances vehicle yaw stability especially in fast evasive maneuvers performed to the safety limit are developed. The driver handles the front steering angle over a turn, while the controller commands the braking forces of individual wheels and rear steering effort. This mitigates the vehicle's oversteer or understeer tendencies during emergent cornering situation. The fuzzy controller is firstly established by qualitative analysis of the dynamics of the vehicle and tires. The available control authority and effect are then evaluated by implementing the controller on the 4WD vehicle model developed before using computer simulation. The simulation results demonstrate the benefit of the proposed control method in terms of improved vehicle response. Specifically, the method is practical for it's simpleness and robustness.