Research On Dynamics And Control Of Vehicle 4WS System

4WS (four wheel steering) is a new technology in vehicle systems. Compared with the current 2WS (two wheel steering), 4WS has such advantages: when the vehicle turns at low velocity, it provides more smaller steering radius and improves the flexibility; when the vehicle turns at high speed, it improves the operation stability.This thesis has the research contents as following:Analyzed on the steering process of 4WS, the characteristic in high speed andlow speed, the different and advantage compare with common 2WS, and theadvantage strategy on breakdown manage.Analyzed the nonlinear factors on 4WS, especially the tyre nonlinear model affects the steering characteristics and stability of the vehicle. A tyre cube nonlinear model is used in robust control of 4WS system. The nonlinear controller is gained, and the rationality and the blemish analyzed too.Based on the hybrid controller of 4WS system and the 2DOF model designed, an implementation scheme is put forward. Analyzed the stable state response and the stabilize factors and the transient state response of 2DOF model. Furthermore, the simulation based on Matlab is done to validate the accuracy of the identification, comes to the conclusion that 4WS can improve the response much.Analyzed some common control models, combined the nonlinear tyre model, a nonlinear 4WS model is put forward. Its stability is analyzed and the result is verified by simulation, and then gave some rationalization advises to later design based on the result of simulate.The last chapter summarizes the research work in this dissertation, and lists the future works in the area.