Research On The Robust Control Method Of Four Wheel Active Steering Vehicle

People are in pursuit of the performance of a vehicle, not only displays in the dynamicperformance of vehicle, and vehicle handling performance. Especially in the current, activesafety performance of automobile more and more attention to people. However, in the activesafety of automobile, the steering system plays a very key role. So many scholars andengineering and technical personnel of vehicle study on deeply active steering system, whichhas developed a system of four wheel steering, active front steering system and four wheelactive steering system. Four wheel steering system is the only control of the car rear wheel, inorder to achieve front and rear wheel steering on the turning contrary in the low speed, theturning radius is reduced the car front and rear wheel steering turn the same in the highspeed,to improve vehicle stability. But the shortcomings of the four wheel steering system iscontrolling solely the rear wheel, it can not control for vehicle yaw rate and sideslip angle atthe same time. Active front steering system based on the traditional front wheel steeringsystem, which added a automatically change the transmission ratio of the control system inorder to realize steering ratio greatly in the low speed, improving the flexibility of car andsteering ratio becomes small in the high speed, improving vehicle stability. Active steeringfront wheel controls mainly the vehicle yaw angle as the control target, the sideslip angle donot be controlled. Four wheel active steering system based on the traditional four wheelsteering system which controlled only on the rear wheels, introduced the active front steeringsystem, to achieve the car front and rear wheel together with active control, become vehiclesideslip angle and yaw rate as the control target. The essence of four wheel active steeringsystem is a collection control system of the active steering front wheel control system andfour wheel steering system, overcoming their respective shortcomings, the realization ofactive steering integrated control system.This paper is mainly aimed at the robust control issue of four wheel active steeringsystem to research. First of all,we set up a mathematical model of two degrees of freedomand interference four wheel active steering vehicle, with active steering control strategy of thesystem, and deduces its feedforward controller. Secondly, using the control Htheory, the feedback H controller is designed. Using MATLAB simulation, through the analysis and studyof the simulation results show that the four wheel active steering system control effect isobviously better. Then using the hybridH2/H control theory, the output feedbackcontroller is designed. Using MATLBA simulation, through the comparison of thesimulation results, the control effect of the output feedback controller for activesteering system designed is better. The last, making the feedback H controller of four wheelactive steering system and the output feedback controller of four wheel activesteering system and traditional four wheel steering system in the same input conditions, byMATLAB simulation, through the analysis of the simulation results shows that the controleffect of output feedback controller is better.