Research On Integrated Control Of Active Front Steering And Active Suspension System Of Distributed Drive Electric Vehicle

With the rapid development of automobile industry and the increasing popularity of automobiles,people put forward higher requirements on the safety and driving experience of vehicles.Therefore,pursuing more superior safety and comfort are the two important directions for the development of automotive technology.As we know,steering system and suspension system,which are the two key sub-systems of the vehicle chassis system,play a critical role in enhancing vehicle stability and ride comfort,respectively.However,it should be noted that the two sub-systems couple with each other through tire force when they work together on the chassis dynamics system,thus a collaborative control problem emerges when the two coupled sub-systems are controlled simultaneously.In this dissertation,the active steering system and active suspension system of distributed drive electric vehicles are studied.Considering the coupling relationship,the following studies for the integrated control between steering system and suspension system have been carried out.Firstly,the vehicle model of 9-DOF and the "magic formula" tire model are established in the MATLAB/Simulink software.And the proven vehicle dynamics commercial software Car Sim is performed to ensure the accuracy of the established models.Secondly,aiming at the dynamic relation of active suspension,the model of suspension system and the road model are established.After establishing the control target of active suspension under different working conditions,the fuzzy PID control algorithm is used to control the ride comfort and roll stability of the vehicle.The simulation results show that the proposed control method is effective in improving vehicle smoothness.Additionally,a 2-DOF vehicle linear model is built for active front steering control.Based on the steady-state response analysis of the vehicle steering dynamics model,the yaw rate and the sideslip angle of the vehicle are taken as the control variables and the control law of additional front wheel angle is obtained by using sliding mode variable structure control algorithm.The simulation in MATLAB/Simulink shows that AFS has a good control effect in vehicle handling stability.Finally,the coupling mechanism of vertical and lateral direction of vehicle is analyzed,and the rule of mutual shadow between vehicle steering system and suspension system is expounded in detail.On this basis,a coordination controller is designed to adjust the control force of the active suspension according to the steering characteristics of the vehicle.And the results show that the effectiveness of the coordinated controller.