Research On Stability Of Distributed Drive Electric Vehicle Based On Four-wheel Steering

The driving torque of four wheels of the ideal yaw angular velocity distributed drive electric vehicle is controlled separately,and the motion state is independent of each other,so it has more controllable degrees of freedom than the traditional vehicle.Based on the distributed drive electric vehicle,this paper studies the influence of four-wheel steering on vehicle stability,constructs the dynamic model of rear wheel steering,and studies the coordinated control strategy of four-wheel steering and four-wheel drive to improve the handling stability of the vehicle at high speed.(1)The car body model and the lateral driver model are built in Car Sim,the driving motor and motor controller model and the longitudinal driver model are built in Simulink,and the distributed driving electric vehicle joint simulation platform is built based on Car Sim and Simulink,which is verified to be in line with the vehicle simulation by the angle step steering condition It is really required that the model can be used to verify the next control algorithm.(2)The stability of the vehicle is analyzed.The yaw rate and the sideslip angle are taken as the evaluation parameters of the vehicle driving stability,and the rear wheel steering control strategy is designed based on the sliding mode control theory.The rationality of the control strategy is verified by the snake driving simulation of the vehicle.(3)Considering that the vehicle stability evaluation parameters are not easy to obtain in the real vehicle test,based on the extended Kalman filter theory,the side slip angle estimation model is designed.Through the double lane change simulation test,it is verified that the sideslip angle estimation model has certain reliability at different driving speeds.(4)Based on fuzzy control theory,a four-wheel steering and four-wheel drive coordinated controller of distributed drive electric vehicle is designed.The side slip angle and yaw rate are taken as control variables to control the rear wheel angle and additional yaw moment required for stable steering.The additional yaw moment is distributed to four driving wheels by the method of differential driving torque of left and right wheels.(5)The open-loop sinusoidal and double lines change closed-loop are selected forsimulation test,compared with the simulation results of four-wheel steering distributed drive electric vehicle and front wheel steering distributed drive electric vehicle,it can be seen that the sliding mode control system can effectively reduce the side slip angle of the four-wheel steering vehicle,and can better control the yaw rate near the ideal value.The four-wheel steering and four-wheel drive coordinated control system not only achieves the expected control objectives,but also has better control effect than sliding mode control system,which greatly improves the vehicle handling stability.