Direct torque control for electronic differential in an electric racing car

This paper presents a new method for development of electronic differentials for electric racing vehicles. Most electronic differential solutions focus on maintaining the vehicle stability as the first and dominant priority, and are designed to keep some stability-related quantity (e.g. wheel slip) in a “safe region”. With racing cars however, the main focus is on the responsiveness of the vehicle and its capability to cope with extreme steering and accelerating demands from the driver. Our focus is on designing a controller to achieve neutral-steer (avoiding over- or under-steer) in race car driving conditions. We show a direct relationship between the steering condition and the difference of the longitudinal tire-road friction forces for the driven wheels. We mathematically derive the desired difference in the tire-road frictions that would achieve neutral-steer and show that it is directly related to the difference in the driving torques provided by motors. A closed-loop-control system is proposed for direct control of the motor torques. The simulation results show a close-to-neutral steering performance of the car (while maintaining its stability) in challenging steering scenarios.