Research On Four Wheel Steering Control System Of Four Wheels Independent EV And Experiment Platform Building

Along with the society pays high attention to environment and energy problem, especially the increasingly serious fog and haze problem, the new energy vehicles gradually become the research focus in the automotive industry. Four-wheel-independent electric vehicle, besides with the energy conservation and environmental protection of electric vehicle, but also has more controllable degrees of freedom that enhances the vehicle stability greatly, so the maneuverability can be greatly improved by completing the special actions such as crab, oblique driving and zero radius turning.A systematic research on control strategies for 4WS vehicle is carried out. And a framework of experiment platform is built. The specific contents of each part are as follows:Firstly, the dynamics analysis of 4WS vehicle is carried out and the linear 2-DOF steering model is established. Then the nonlinear vehicle model is established based on the nonlinear tire model. The common feedforward control and yaw rate feedback control were analyzed separately, and their shortcomings are put forward.Secondly, in view of the defect of two common 4WS control, this chapter establishes an ideal steering vehicle model and designs a LQR controller to control the active 4WS system. The simulation results show that the active 4WS based on LQR control can not only control the side slip angle to zero, but also track the ideal yaw velocity, which improves the vehicle handling stability.Thirdly, on the basis of the linear 2-DOF 4WS model, considering the nonlinear tire model and the independence of the 4WS, a nonlinear 4WIS fuzzy controller based on side slip angle and yaw velocity feedback is designed. The simulation results show that the 4WIS system based on fuzzy control can reflect the actual running state. On the basis of ensuring zero side slip angle, it can improve the operability at low speed and stability at high speed.Finally, referring to research results of experimental platform, this chapter analyzes and compares the three experimental platform and choose a platform as the final structure. A system design of four-wheel independent platform is carried out. Various parameters of the system are selected and the stress distributions of various conditions are analyzed. At last, each subsystem of the platform is introduced, and some simple tests of the platform are carried on.