MPC-Based Slip Ratio Control for Electric Vehicle Considering Road Roughness

In this paper, a slip ratio controller based on model predictive control (MPC) considering road roughness is proposed for electric vehicle (EV) to improve the driving/braking performance under low adhesion coefficient road. A half vehicle dynamic model is derived in which pitching, wheel rolling, and tire vertical movement is taking into account. The influence of vertical force variation caused by road unevenness and tire load transfer is analyzed to design slip ratio controller. In order to ensure vehicle safety, wheel slip stable zone is considered as time-domain constraints of the nonlinear-MPC. Besides, the motor output torque is limited by the motor maximum torque, which is considered as system time-varying constraints. The control objectives include vehicle safety, good longitudinal acceleration and braking performance, preservation of driver comfort, and lower power consumption. The proposed slip ratio controller is verified on a 13-degree-of-freedom (13DOF) EV model in MATLAB/Simulink. Simulation results of different maneuver on roughness surfaces show the benefits of the controller.