Research On Automatic Parking Control Strategy Considering Tire Transient Characterist

With the continuous improvement of the urbanization level and the continuous increase of the number of cars owned by thousands of people,the problem of urban parking becomes more and more serious,which leads to many traffic safety accidents.The automatic parking function in the advanced auxiliary driving function can effectively solve the problem of difficult parking.Aiming at the automatic parking path tracking control technology,this paper studies the vehicle dynamics model considering the transient characteristics of the tire,and studies different control strategies for different parking scenarios,and proposes the automatic parking model predictive motion control strategy considering the tire lag.Firstly,the transient characteristics of low speed tire are studied.The transient model of the relaxed length tire and the transient model of the dynamic deflection tire were established,and the dynamic analysis and frequency response analysis were carried out.The lateral force lag phenomenon caused by the transient characteristics of the tire was described.Secondly,based on the transient model of the low speed tire,a lateral dynamics model considering the transient characteristics of the tire was established.The responses in frequency domain and time domain were compared and analyzed with the traditional vehicle geometric model,kinematics model and 2-DOF vehicle model.The improved vehicle dynamics model can better show the phenomenon of vehicle steering lag caused by the transient characteristics of the tire in low speed conditions,improve the accuracy of the vehicle dynamics model,and provide a model basis for the design of automatic parking controller.Finally,the control strategy of automatic parking with tire lag is studied.In order to compensate steering lag,based on the model predictive control theory,the vehicle dynamics model considering the transient characteristics of the tire was taken as the prediction model,and the tire lag was considered in the prediction of the vehicle state and the optimization calculation of the front wheel Angle control,so as to make up for the lag of the lateral response of the vehicle.Joint Car Sim and Simulink simulation platform is established,in parallel parking scenario and vertical parking path tracking simulation experiment was carried out in the scene,and not considering the MPC controller of tire hysteresis comparison analysis,the results show that the tire hysteresis of MPC controller can compensate for steering lag phenomenon,improve the control precision of the automatic parking system.