Differential Speed Steering Control for Four-Wheel Distributed Electric Vehicle 2019-01-1235
In order to perform differential control instead of the mechanical differential and improve the steering performance of distributed electric vehicles, a two-level differential speed steering control strategy is proposed. Firstly, the yaw rate tracking upper-layer controller is designed based on PID feedback and looking-up table model, which can shorten response time and reduce the impact of vehicle model parameters mismatch. Then, In order to improve the robustness to external disturbances and uncertainties, a wheel speed tracking lower-layer controller is devised based on integral modified reaching law sliding mode control algorithm. Eventually, three simulations were conducted to validate the control strategy. The first simulation results indicate that the proposed strategy can properly distribute driving torque and coordinately control the inner and outer wheels running at different speed to improve vehicle handling stability when the vehicle is steering under the conventional steering system. Moreover, when the conventional steering system fails in the second simulation, the proposed strategy can independently control the vehicle movement direction to prevent it from losing steering function. The last simulation results show that the proposed strategy can also be superimposed on the conventional steering system for differential speed assisted steering to improve the steering performance of distributed electric vehicles.