Lane Change Trajectory Planning And Tracking Control For Autonomous Vehicles

In the process of changing lanes at high speed,frequent traffic accidents seriously endanger the life safety of passengers.The research on lane change trajectory planning and tracking control of autonomous vehicles can effectively avoid the occurrence of traffic accidents.In order to make the autonomous vehicle change lanes safely and improve the safety of the road traffic system,this paper studies the trajectory planning and tracking control respectively for the two driving conditions of free lane change and forced lane change in the high-speed driving environment.The specific contents include:(1)Dynamic modeling in Frenet coordinate systemConsidering the three coordinate systems comprehensively,ignoring the air resistance,through Newton’s second law,the force of the vehicle when changing lanes is analyzed,and the dynamic model under the vehicle body coordinate system is established.In order to facilitate the description of the driving trajectory,a dynamic model in the Frenet coordinate system is established by transforming the coordinates,which provides a theoretical basis for the design of the trajectory tracking control algorithm.(2)Lane change trajectory planning of autonomous vehiclesAiming at the problem that the quintic polynomial lane change method only plans the lane change trajectory at the initial moment,this paper establishes a quintic polynomial lane change trajectory model based on the boundary conditions of the driving environment.The lane change trajectory planning is decoupled into lateral and longitudinal trajectory planning.Considering the lane change performance indicators comprehensively,a lateral trajectory optimization model is established.The optimal lane change duration is obtained by Pontryagin’s minimum principle.The continuous-time longitudinal motion equation is discretized to establish a prediction model,and the longitudinal velocity is rolled and optimized through the model predictive control algorithm,so as to achieve the goal of dynamic lane change.(3)Lane change trajectory tracking control of autonomous vehicleAiming at the problems of large amount of calculation and poor robustness of trajectory tracking control algorithm,this paper decouples the lateral and longitudinal trajectory tracking,so as to reduce the amount of calculation.Using the experimental method,the accelerator / brake calibration table is made,and the longitudinal trajectory tracking control is carried out by double PID controller.The Ackermann formula is used to design the control function,and the sliding mode switching function is replaced by the fourth state quantity of the state vector.It is proved that when the motion point of the system reaches the sliding mode surface,the system is not affected by external disturbances and has good robustness;It is proved that the system can reach the sliding mode surface in finite time by Lyapunov function.(4)Simulation verification of two lane change scenarios in high-speed driving environmentThrough the co-simulation of Matlab/Simulink,Prescan and Carsim,respectively,the lane change trajectory planning and tracking control of the autonomous vehicle are simulated and verified.The simulation results show that the quintic polynomial trajectory planning method incorporating the model predictive control algorithm can effectively dynamically plan the lane change trajectory.The trajectory tracking controller of the integrated sliding mode variable structure control algorithm and the double PID algorithm has strong robustness and can effectively control the lane change vehicle to drive smoothly along the desired trajectory.