Simulation Study On Lateral Stability Coordination Control Of A Four-Wheel Steering Off-Road Vehicle

Four-wheel steering system(4WS)is one of the important means to improve the steering performance of automobiles.Electronic stability control system(ESC)can improve the steering stability of automobiles under extreme conditions.This paper focuses on the coordinated control of these two subsystems,in order to improve the stability of the vehicle under steady-state conditions while ensuring the 4WS vehicle have similar handling with the front-wheel steering vehicle,When ESC starts to work under limit conditions,the two subsystems can coordinate to ensure stability.The identification of limit conditions and the control strategy of four-wheel steering under steady and limit conditions were studied.This paper is based on Simulink + Trucksim software co-simulation analysis,Simulink software was used to build control strategy model,Trucksim software was used to build dynamic model.In order to judge the lateral stability of vehicles,the representation-state of lateral stability and the criterion of lateral stability were analyzed.The sideslip angle of the center of mass and the friction coefficient of the pavement,which were used in the judgment and control of lateral stability but cannot be obtained directly,are estimated.Based on the nonlinear three-degree-of-freedom four-wheel plane dynamic model,the sideslip angle of the center of mass was estimated by the extended Kalman filter method,and the road friction coefficient was estimated based on the parameters of the lateral dynamic state.The simulation results show that the estimation methods are effective.The control strategy of 4WS under steady state condition was studied.Zero-centerof-mass sideslip angle control and fuzzy control were adopted,simulation was done to compare the two control methods.The results show that the four-wheel steering vehicle with fuzzy control has smaller sideslip angle,higher stability and can maintain ideal yaw rate response.For ESC working independently,in order to simulate its effect,a control model of ESC was built by proportional feedback control.The control strategy of 4WS when ESC system starts to work under limit conditions was studied,yaw rate error was used as the mode switching judgment parameter.The strategy is rear wheel alignment stopping steering under extreme conditions and add transition control of rear wheel when the control mode switching from steady state to extreme conditions.The simulation results show that the method can make the lateral stability of vehicle unchanged while the rotation angle of rear wheel decrease steadily during mode switching.