Study On Variable Steering Ratio And Active Steering Control Strategy Of Steer-by-wire System

The steer-by-wire system of the vehicle could control it with variable steering ratio andactive steering according to the traffic state of the vehicle. The handing stability of the vehiclewill be improved. And it is of grate significance to the vehicle active safety control. Thevariable steering control and the active steering control of steer-by-wire system are researchedin this paper.This paper study is based on the project supported by the National NaturalScience Foudation(51305190).First of all the structure and the working principle of the steer-by-wire system areanalyzed in this paper. The dynamic differential equations of the parts of steer-by-wire systemare determined. The model of the steer-by-wire system is built by the using ofMatlab/Simulink. This model is embedded in the vehicle model of CarSim. So the model ofsteer-by-wire vehicle is built.The second, the concept of variable steering ratio is proposed according to thecharacteristics of the steer-by-wire system. Two kinds of methods to determine the variablesteering ratio are researched. The value of the yaw rate gain is optimized in view of thedifferent methods. Then an ideal variable steering ratio is eventually determined.Thirdly, the active steering control with fixed steering ratio based on the feedback of yawrate is researched. The adaptive fuzzy PI controller is designed. The model of active steeringcontrol is built. And it is combined with the control strategy of variable steering ratio. Thenthe active steering control with variable steering ratio control strategy is formed.Finally, the driving simulator of steer-by-wire vehicle is built on the basis of thetraditional vehicle driving simulator. The control strategy of variable steering ratio is verifiedby subjective evaluation. And the active steering control strategy is tested in different workingconditions.