A Novel Control Strategy of Straight-line Driving Stability for 4WID Electric Vehicles Based on Sliding Mode Control*

Aiming at the stability problem of four-wheel independent drive (4WID) electric vehicles in straight-line driving on low-adhesion roads, a novel sliding mode control strategy is proposed to improve the safety and stability of the vehicle. A 7-degree-of-freedom dynamic model of the vehicle is firstly established and the stability situation is analyzed. According to the analysis results, an additional yaw moment controller based on sliding mode control (SMC) is designed. The yaw angle, yaw rate and lateral displacement are selected as the control variables, and the bilateral adjustment method is adopted to adjust the vehicle attitude in time and prevent vehicle deviation. A slip rate controller based on PID control is also designed to improve the stability margin. Based on the Carsim-Simulink co-simulation platform, the strategy was verified under the conditions of uniform low-adhesion roads and split roads. Simulation results indicate that compared with no control strategy, the proposed strategy has achieved better results and can effectively improve the straight-line driving stability of vehicles.