Dynamics Characters And Robust Control Of Vehicle 4ws System

The vehicle Four-Wheel Steering (4WS) technology is an advanced technology,which has a very hopeful future in application. As an effective means to improve thevehicle handling stability, 4WS technology is widely accepted. Current research aboutvehicle steering technology is mostly based on the certain model, and the uncertainfactors and nonlinear factors in vehicle steering system are not sufficiently considered.In order to solve this problem, we put forward our research work. Firstly, in this paper, by introducing vehicle four wheel steering systemmechanical model, driver regulation model and the effect of rear tire on the steeringactivities, we build a driver/vehicle/road closed loop 4WS nonlinear model with fivedegrees, which is based on the abundant analysis of the nonlinear factors and theuncertain factors of vehicle. At the same time, we qualitatively analyze the abovemodel with modern nonlinear dynamical theory, and point out the effect of the varietyof bifurcation parameter (vehicle velocity) on the stability of the vehicle 4WS. Secondly, based on the environment disturbance and the variety of tireparameters, we build vehicle 4WS uncertainty model respectively. And in order toimprove the robustness of the system, we do the theory analysis and the optimalcontrol design with the robust H∞ control theory. Furthermore, aiming at theuncertain model based on the environment disturbance, we do the synthesis controldesign for the vehicle 4WS system by using the mixed H2 / H∞ optimal controltheory and the LMI method. In this way, we can not only assure the system integralperformance, but also promote the system disturbance attenuation performance. Atlast we do the simulation and computation. The result indicates that the control effectis obvious and the work we do has some directive meaning for the actual engineering. Lastly, we synthetically consider the effect of the uncertain factors and nonlinearfactors on the stability of the vehicle 4WS system, and build a vehicle 4WS systemnonlinear uncertain model. Moreover, we analyze and simplify this model withnonlinear robust control theory. Based on this, we design the nonlinear robustcontroller and do the simulation validation. The result shows that it has good controleffect. In conclusion, in this paper based on the uncertain factors and the nonlinearfactors, we do the control design with modern robust control theory. And what we dowill be a base of further research work on 4WS. This paper is supported by the National Natural Science Foundation of China(No.50075060).