The Design Of State Observer Of Four-wheel Steering Vehicle And Stability Simulation And Analysis

With the improvement and development of today's road traffic system and vehicle manufacturing,the average speed of vehicles driving increases gradually,high-speed driving safety problem increasingly prominent.According to the investigati-on and analysis,the traffic accidents under the high-speed driving caused by the vehicle steering stability problem quantity proportion have larger growth momentum.Firstly,based on U.Kiencke,L.and Nielsen,s two-track vehicle dynamic model,this article study 4WS vehicle's non-linear modeling.The above vehicle model can be reduced to the linear single track model of this article for small body side slip angle and constant vehicle body speed over a limited time range by neglecting inclination and wind forces and assuming there is no difference between the left and right track.Then a 4WS feed-back control system,which regards yaw rate as feedback,is established based on the single model and emulated under the environment of Simulink.Simulation experiments verify the 4WS control system's stability and driveability.Next a 4WS optimal control system,which regards front-wheel steering angle as optimum size,is also established based on the single model and emulated under the environment of Matlab.Simulation experiments show the 4WS optimal control system's better stability and control performance than feedback control system's.However,the above two control methods acquire sound control effect,but they all ignore the possible external interference,model uncertainties and other factors that are ignored in a real world application.Thus to achieve the anti-jamming performance in the actual use,we must consider the existence of interference which is not easy to measure with sensors.So this paper designs a sliding mode disturbance observer based on yaw moment control to estimate the equivalent external disturbance.The actual situation can be basically restored by this estimate.At last,simulation program is compiled in M script files by MATLAB,and the simulation results verify the effect of tracking in different road surface friction coefficient and different body center of mass velocity.The simulation analysis results also verify the feasibility of the observer.