Coordinated Control of Tractive and Braking Forces Using High Slip for Improved Turning Performance of an Electric Vehicle Equipped with In-Wheel Motors

This paper describes development of coordinated control of tractive and braking forces using high wheel slip in order to enhance turning performance of electric vehicle equipped with in-wheel motors. In the case of conventional vehicle, turning radius is definitely limited by kinematic features with respect to wheel base, maximum steering angle and track width of the vehicle. Military and special purpose vehicles are required to overcome turning radius limitation in order to conduct urgent and emergency tasks and avoid enemies rapidly. The control purpose is achieved by minimizing lateral tire force of rear wheels using excessive wheel slip condition. It is possible for the vehicle to turn around central turning point using the proposed algorithm. The center turning point is defined based on the driver's intention. The coordinated control algorithm consists of three parts: an upper level controller that computes the desired net force and moment in order to make one point turning motion, a lower level controller distributes tractive and brake input torques of each wheel for excessive slip control and sensor/estimator provides vehicle information to controllers. Computer simulations have been conducted to evaluate performance of the proposed control algorithm. It has been shown from simulation results that turning performance can be significantly improved.