Research On Multi-objective Sliding Mode Control For Vehicle Lane-changing Trajectory Tracking

As one of the development trends of the "five modernizations" of automobiles,intelligent cars change people’s lives.On the one hand,they can make people travel more safe and convenient.On the other hand,intelligence enhances the development of the automobile industry.In the actual traffic environment,lane-changing is more likely to cause traffic accidents.In order to improve driving safety during lane-changing,multi-objective sliding mode control for lane-changing trajectory tracking is studied in this thesis.This thesis designs a multi-objective sliding mode control system for trajectory tracking.Firstly,aiming at the tracking control of lane change trajectory,this thesis uses the quintic polynomial to plan the feasible lane change trajectory,and designs a sliding mode controller for multi-target trajectory tracking.According to the vehicle two-degree-of-freedom dynamics model and trajectory tracking error model,the trajectory-tracking vehicle dynamics model based on the desired trajectory is established.On this basis,a sliding mode controller for multi-objective trajectory tracking is built,which has a better trajectory-tracking effect.Aiming at the obvious "chattering" phenomenon in sliding mode control systems,a BP neural network is proposed to adjust the sliding mode law according to the real-time state of the vehicle,which optimizes the sliding mode controller and weakens the "chattering" phenomenon.The effectiveness of the proposed trajectory tracking controller is verified by Simulink/Car Sim joint simulation.Then,aiming at the yaw stability problem caused by vehicle lane-changing,a layered control system is designed.Firstly,an upper layer fuzzy controller is designed,which collects the expected,actual yaw rate and mass-center information of the vehicle at each moment.By designing fuzzy rules that meet the requirements,the upper controller can estimate the required yaw torque correction to maintain yaw stability.Then,according to the differential braking force distribution method,the lower-level controller for braking torque distribution is designed.This controller can distribute different braking torques to the wheels,thereby causing the vehicle to generate additional yaw moment estimated by the upper-level controller.This improves the yaw stability of the vehicle.By the Simulink/CarSim joint simulation,it is verified that the designed control system has a good trajectory tracking and yaw stability performance.Finally,on the hardware-in-the-loop experiment platform,the control system algorithm is compiled and loaded into the real controller to carry out the quintic polynomial lane-changing trajectory tracking experiment.Through the hardware-in-the-loop experiment,the effectiveness of the designed control system is verified.