Study Of Manipulate Stability For Four-Wheel Steering Automobile

The automobile four-wheel steering (4WS) is normal front wheel steering, besides, rear wheel steering is included accordingly. The main target of high-speed stability, side wind process stability, low-speed maneuverability flexibility and high-speed turning radius is improved for 4WS vehicle. Since the last stage of 1970s, the 4WS system has been begun to research abroad. The research of vehicle's operation stability entered into a new phase after the first use of 4WS system in 1985.This paper constructively modeled a nonlinear vehicle's four-wheel steering model, a five degree of freedom system, which is based on the analysis of the nonlinear characters of vehicle system and includes a model of driver regulation and the effect of rear tire on the steering activities. This model is a typical model and is more practical than any other models, because we take account of many nonlinear factors in the vehicle system.This paper speaks volumes for 4WS vehicle is better than 2WS vehicle in operation stability, which does relatively system theory analysis by using stability theory.This paper takes a deep research on the nonlinear 4WS model by using modern nonlinear dynamics stability theory, Hopf bifurcation theory. The operation stability of 4WS vehicle is analyzed. The condition leading the Hopf bifurcation and the normal form of Hopf bifurcation are deduced. It also got a way to judge the stability of period solution to the model.This paper simulates the 4WS and the 2WS systems numerically under all kinds of conditions, discusses the effect of different parameters on vehicles stability, supplies and tests the study theory of nonlinear vehicle's four-wheel steering model, applies the numerical simulation method of vehicle's steering stability.This paper is also a base of further research work on nonlinear 4WS, because the theory and numerical methods in it and many tire model, driver model and steering model in it.