Wheel Velocity Based Cascade Driving Force Control for Electric Vehicles

Although driving force control (DFC) has been shown a promising traction control strategy, its practical application is still limited due to the following reasons. First, it is required to use the vehicle chassis velocity to calculate the wheel velocity reference. Second, almost all the existing studies merely utilize the integral force controller without consideration of the windup phenomenon. Third, no stability condition has been proposed to design the controllers systematically. To address the above issues, this article proposes a new cascade configuration for DFC of electric vehicles. The outer layer controls the driving force and directly generates the wheel velocity reference for the inner layer without using the vehicle chassis velocity. The driving force is controlled by an antiwindup proportional-integral controller. Based on the circle criterion, this article establishes a practical oriented stability condition that can be checked conveniently via graphical tests. The effectiveness of the proposal was validated using an electric vehicle developed by our research group. In comparison with the DFC system that employs the conventional integral force control without antiwindup, the proposed approach achieves a 70% reduction in the overshoot at a sudden increase of road friction condition.