Control strategy of four-wheel independent drive electric vehicle based on vehicle velocity estimation and switchover

Abstract

The four-wheel independent drive electric vehicle (4WID EV) has some advantages, such as independent control of torque, easy measurement of torque, and multiple drive modes, the most significant of which are four-wheel drive and two-wheel drive modes. However, there is a problem with the switched drive mode, which would have an adverse effect on the precision of vehicle velocity estimation, the vehicle stability and comfort. In order to solve the problem, a control strategy with a switched drive mode is proposed. The control strategy is based on two vehicle velocity estimation algorithms. Between the two vehicle velocity estimation algorithms, the vehicle velocity estimation algorithm based on an unscented Kalman filter is designed in a four-wheel drive mode condition, whereas the vehicle velocity estimation algorithm based on the wheel rotational speed is designed in a two-wheel drive mode condition. Switchover of the two vehicle velocity estimation algorithms would cause a vehicle velocity saltus step, which has an adverse effect on vehicle control, so a vehicle velocity smoothing algorithm is proposed. Simulation results show that the control strategy not only reaches a high vehicle velocity control accuracy, it also improves the vehicle stability as well as the comfort. Furthermore, the results show that the proposed strategy can achieve stabilization with disturbance.