Optimum tyre force distribution for four-wheel-independent drive electric vehicle with active front steering

Tyre workload is widely used as performance index in tyre force distribution. The existing methods are limited by either the uneven distribution result or too many constraints. To maximise vehicle stability margin while not involving too many constraints, an optimum tyre force distribution method based on minimising the variance and mean value of tyre workload for four-wheel-independent drive electric vehicle with active front steering (AFS) is proposed. The operations of driver are explained as the desired total longitudinal and lateral force and yaw moment constraints. The four longitudinal tyre forces and the lateral force of the front axle are obtained by using quasi-Newton method for solution. The simulation results show that the proposed method can increase the maximum safe speed by several percents when compared to the existing methods. Vehicle test verifies that the adhesion margin of the vehicle is kept to a high level, which will enhance the stability performance.