Research On Autonomous Lane Changing Strategy Of In-wheel Motor Drive Electric Vehicles

With the increase in car ownership,various environmental problems with it have become increasingly prominent.China is initially scheduled to ban the sale of fuel vehicles in 2030,so research on pure electric vehicle technology has gradually become the focus of attention from all walks of life.As one of the hotspots of current electric vehicle research,the in-wheel motor drive electric vehicles has the advantages that traditional fuel vehicles do not have.Its four wheel-driven wheel motors can be independently controlled.With the development and application of intelligent related technologies in automobiles,autonomous vehicle lane changing has become a hotspot in current research on autonomous driving of vehicles.When a vehicle is driving on an expressway,lane changing is a frequently occurring vehicle behavior.Road jams and traffic accidents often occur during the vehicle's lane changing process.Therefore,it is very meaningful to study the autonomous lane changing strategy of the highway.In addition to geometric constraints of roads and road surface adhesion coefficients,vehicles are also constrained by vehicle actuators and kinematics.Because the vehicle autonomous lanechanging strategy studied in this paper is based on the highway lane-changing scenario,the dynamic constraints of the vehicle during the lane-changing process must also be considered.Because multiple constraints exist in the vehicle's lane changing trajectory tracking process,the traditional control method cannot deal with it well.Therefore,this paper uses the MPC trajectory tracking controller to achieve trajectory tracking in the vehicle's autonomous lane changing strategy.The main research contents of this article are:1.Modeling of in-wheel motor drive electric vehicles.In view of the characteristics of the four-wheel independent drive of the in-wheel motor drive electric vehicles,this paper completed the modeling of its vehicle model through Carsim and Matlab / Simulink software.First,the working principle and mathematical model of the brushless DC motor used are analyzed;then,the drive control strategy and regenerative braking control strategy based on torque closed-loop control are designed to accurately control the torque of the hub motor;second,for the Designed torque control strategy,built its control model in Simulink and conducted simulation verification.The simulation results verified the effectiveness of the torque control strategy;finally,after modifying the transmission system and braking system of the vehicle model in Carsim,connect The control system model included in Simulink completes the construction of the in-wheel motor drive electric vehicles model,and is compared with the original vehicle model in Carsim to verify the simulation.The simulation results show that the designed in-wheel motor drive electric vehicles model can be used in the vehicle in this paper Research on autonomous lane changing strategy.2.Research on vehicle autonomous lane changing strategy.The autonomous lanechanging strategy designed by this paper is aimed at the scene of vehicles changing lanes on the expressway.The entire lane-changing process takes less time,and the vehicle generally maintains a stable driving speed.First analyze the characteristics of the vehicle's lane-changing behavior,design a simplified lane-changing scenario to study the vehicle's autonomous lanechanging strategy;then analyze the minimum safety distance and lane-changing motivation during the lane-changing process;and finally,compare the different constraints based on the trajectory planning The trajectory planning method is a five-degree polynomial planning method suitable for the trajectory planning of the vehicle's autonomous lane-changing strategy in this paper.3.Research on trajectory tracking control method based on AFS and DYC coordinated control.First,the AFS controller and the DYC controller are designed based on the fuzzy logic control theory,and the driving force distribution controller is designed for the characteristics of the four-wheel independent drive of the in-wheel motor drive electric vehicles;then,the AFS and DYC are generated due to the mutual coupling For the mutual interference problem,the coordinated controller of AFS and DYC is designed based on the steady state boundary.When the steady state boundary index is within the steady state boundary,the AFS controller works.When it exceeds the steady state boundary,AFS and DYC work together.And coordinate the output;again,on the basis of analyzing the basic principles of MPC,a three-degree-of-freedom monorail model of the vehicle is established as the prediction model of the trajectory tracking controller;finally,combined with various constraints when the vehicle changes lanes,based on the linear time-varying prediction model,The required trajectory tracking controller is established.4.Simulation and verification of vehicle autonomous lane changing strategy.First,the AFS and DYC coordinated controllers are simulated and verified.The simulation results show that the coordinated controllers can improve the stability and trajectory tracking capabilities of the vehicle.Second,to verify the performance of the MPC trajectory tracking controller,the electric vehicle is driven based on the wheel hub.The model is compared with the optimal curvature preview controller.The simulation results show that the tracking error of the MPC trajectory tracking controller is smaller and the effect is better.Finally,the vehicle autonomous lane changing strategy is simulated and verified.The effectiveness,reliability and robustness of the vehicle's autonomous lane-changing strategy were verified under the conditions of constant speed of the vehicle,stationary of the front vehicle and different speed conditions.