The Lateral Movement Research And Comparative Analysis Between Front Wheel Steering And Four-wheel Steering Vehicle

With the development of “intelligence” and “motorization” of automobiles,higher requirements are put forward for the active safety technology of automobiles.Lateral motion control system is an important system in the active safety system to ensure the lateral motion stability and safety of the vehicle.The research on vehicle lateral motion control system is finally attributed to the control research of steering system.Therefore,this paper studies and compares the lateral motion control of front wheel steering system and four-wheel steering vehicles.Supported by the National Natural Science Fund Project “Research on Control Mechanism and Evaluation Method of New Type of Wire-Controlled Steering System Based on Driver Characteristics”(Number:51575223)and commiting to research and compare the lateral motion stability and path tracking performance of front wheel steering and four-wheel steering vehicles.The lateral preview deviation and the automotive center-of-gravity angle are the target parameters,and the controller is designed by the sliding mode control algorithm to realize the tracking of the target path when the vehicle is turning,and at the same time ensure the stability of the vehicle.When the vehicle status parameter changes or there is a disturbance,the sliding mode adaptive controller is designed to improve the robust performance of the vehicle against interference.The strategies are verified by co-simulation experiments between Car Sim and MATLAB/Simulink.Main research content is as following:1.The vehicle dynamics model and the lateral preview deviation model are established based on MATLAB/Simulink.Modeling the front-wheel steering vehicle and the four-wheel steering vehicle,first researching the vehicle dynamics model and the tire model,then establishing the tire model of the “magic formula” and analyzing the influence of the tire parameters on the tire characteristics;The two-degree-of-freedom model of the front wheel steering vehicle and the four-wheel steering vehicle is established respectively,and a mathematical model of lateral preview deviation is established according to the parameters of the angle between the tangent of the road centerline and the longitudinal axis of the vehicle,the preview deciation,and the distance deviation between the vehicle center of mass and the road tenterline.The reliability of the established vehicle dynamics model is verified.2.Research on vehicle steering control strategies.The control strategy of the front wheel steering system and the four-wheel steering system is studied.Firstly,the traditional steering system is simulated under the corner control strategy,yaw rate control strategy,yaw rate and front wheel angle integrated control strategy.On the basis of the control effect of the control strategies,the front wheel angle feed-forward and yaw rate feedback control are applied to the four-wheel steering system;the driving simulator experiments are carried out on the three control strategies of the front wheel steering system and the control strategies of the four-wheel steering system.On this basis,the trajectory tracking performance and steering stability of the lateral motion control of the two systems were compared and analyzed.3.Research on vehicle lateral motion control algorithm.Based on the simulation and comparison analysis of the traditional steering system and the four-wheel steering system,the above control strategies don't take into account the impact of the parameter changes of vehicle state and the external disturbances.Therefore,in order to improve the ability of the controlled vehicle to resist interference and ensure the stability and safety of the vehicle lateral motion control,the lateral preview deviation and the automotive center-of-gravity angle are used as the control targets,the coupled and uncoupled controllers are designed by the sliding mode control method and the sliding mode adaptive control method,and the stability of the controllers are analyzed by Lyapunov's law of stability.4.Through the MATLAB/Simulink and Car Simco-simulation platform,the controllers designed by the sliding mode control algorithm and the sliding mode adaptive control algorithm are compared and analyzed in multiple working conditions;In order to verify the stability and robustness of the control method,the road simulation experiments of perturbation of different longitudinal vehicle speed changes and external disturbances with different adhesion coefficients are carried out.The results reveal that the proposed control method can effectively improve the lateral motion stability of the controlled vehicle,has better path tracking ability,and has good robustness to longitudinal vehicle speed and external disturbance.