Research On Dynamics Analysis And Control Strategy Of Steer-by-wire System For Automotive

Steering system is an important device for controlling the vehicle driving route and direction,and its performance directly affects the operation of the vehicle driving stability and safety.Unlike traditional steering system,steer-by-wire system does not have mechanical structure between the steering wheel and steering wheels.The control unit analyzes the vehicle running state and determines the best front-wheel steering angle in current state.Then the steering motor controls the steering motor to rotate,to complete turn movement.When better control system parameters selected,the sensitivity of the steering and handling can be greatly improved.Meanwhile,steer-by-wire system controls the steering wheel applied to the right steering torque,according to vehicle operating state,so the driver can get more information about vehicle running status.So many advantages make it the future direction of the vehicle steering system.Through the analysis of steer-by-wire system,steering control and torque feedback control strategy have been designed.According to relevant national standards and vehicle steering test experimental data,a variable steering rate control strategy has been designed to make the performance of vehicle yaw rate change better in steering state.According to actual vehicle operating conditions and the steering yaw rate difference under ideal conditions,the vehicle handling and stability control strategy have been designed.It can make the vehicle under the disturbance quickly restore the original operating state,to ensure traffic safety.After contrasting the torque on the steering wheel in the real condition and ideal condition,the feedback torque control strategy have been designed.Its value depends on the summer of the torque on the steering wheel in the ideal condition and the value that comes from the steering yaw rate.So the feedback torque is in ideal state and can perform the actual running state at the same time.So that the driver in a comfortable condition can get more "road feel."Matlab/Simulink is used to create simulate model of steer-by-wire system.In the two degrees of freedom vehicle simulate model,the variable steering ratio control strategy is verified.In the three degrees of freedom vehicle simulate model,the stability control strategy is verified under a lateral force action.And in the with two degrees of freedom vehicle simulate model,"road feel" control strategy is verified.After the design and verification of steer-by-wire system control strategy,it is found that steer-by-wire system can significantly improve handling and stability.The driver can get better "road feel" under the control of feedback torque control.