An Acceleration Slip Regulation Strategy for Four-Wheel Independent Drive EV Based on Road Identification

Four-wheel independent drive EV is driven by four brushless DC motors which are embedded in the wheel hubs. It enables each wheel's driving torque to be controlled independently. Due to the motors' torque and rotational speed easily measured, as well as the features of fast response and precise control, the EV enjoys obvious advantages over traditional vehicles in acceleration slip regulation. In this paper a novel acceleration slip regulation strategy for four-wheel independent drive EV is studied. The strategy includes a road identification module for the peak value of road adhesion coefficient and a slip regulation logic based on PID algorithm. Through comparing the current wheel slip ratio and the utilized adhesion coefficient with the typical roads' value, the identification module adopts the fuzzy control algorithm to recognize the similarity between the current road and the typical roads. Utilizing the similarity we can calculate the optimal slip ratio of the current road. Based on the difference between the current value and the optimal value, the slip regulation logic adopts increment PID algorithm to make all the wheels quickly response the optimal slip ratio. One important thing to note about this method is that the algorithm of tracking optimal slip ratio on split road may cause the driving forces between the left and right wheels inconsistent, and affect the stability of the vehicle. To solve this problem, in the acceleration slip regulation algorithm, we set that once the vehicle's speed exceeds a certain value, a low-election strategy will be introduced to distribute the driving forces of the left and right wheels, so the same driving force can be obtained. Finally the proposed strategy is verified in the co-simulation environment between MATLAB / SIMULINK and Carsim.