Study Of Control Methods For Automobile Electric Power Steering System Based On Sliding Mode Control Algorithm

With the traffic scenario improved and automotive control technology developed,automobile,one of the widely used vehicle,is highly required as to controllability,safety,stability and comfortability.In addition,the driver’s driving experience and safety are all down to the EPS system,which is recognized as an essential part of automotive steering system.What’s more,many strengths of the EPS system has made it something for research.Having studied vehicle model,this essay conducts simulation analyses on performance of EPS system by sliding mode control theory applying to mathematics model,which will be demonstrated in this essay by the following parts:A.The construction of EPS system model.EPS system is divided into three modules: a.control unit;b.motor model: DC brush motor model is adopted;c.Mechanical structure model: mainly involved are steering wheel model,upper steering column model and lower steering column model.B.The analysis of the control strategy of EPS system.The functional analyses on EPS system could identify its operation mode first,according to which corresponding control strategy is then developed,namely assist control mode,Positive control mode or damping control mode.C.Control strategy and the construction.In the premise of assist control mode,what is foremost is to identify the operation mode by steering wheel torque value.Using the assisting characteristics curve,assist current target value then could be calculated by the current driving speed and steering wheel torque value.This essay introduces fuzzy sliding mode control algorithm and that GA could optimize the switch gain of sliding mode so as to reinforce the robustness of EPS system and to decrease the chatter of SMC.In the premise of Positive control mode,this essay introduces dual closed-loop PID control strategy to improve the return-to-centre performance of steering wheel.Firstly,the operation mode could be identified by steering wheel angel,its differential value and its torque value.Additionally,the difference of the positive steering angel and its target value is input into the EPS system and then the designed “angel-current” dual closed-loop PID control strategy.Consequently,the return-to-centre performance is enhanced.D.The resulting analyses of the EPS system.In the case of the two control modes mentioned above,simulation model of EPS system is first constructed on Simulink in this essay and then simulation experiments are conducted on this model to prove the designed control strategy.