| At present,the traffic safety problem is increasingly prominent,and the lane change(LC)maneuver is one of the important factors that cause motor vehicle collision.Autonomous vehicles can reduce traffic accidents caused by human factors,especially in the process of LC execution.Autonomous vehicles’cooperative LC has become a key technology to improve safety of vehicle LC maneuvers.In this paper,the priority criterion was constructed based on the conflicting conditions between the lane change vehicle and the front obstacle vehicle.According to the priority criterion,trajectory planning and tracking control method for autonomous vehicles’ cooperative LC are constructed,including the strategy of vehicles’horizontal and vertical trajectory adjustment during cooperative LC process under different working conditions,and the corresponding trajectory tracking control method.The aim of this research is to make LC maneuvers more safe,stable and comfortable.Firstly,based on the theory of optimal LC trajectory,the passengers’ comfort,vehicle stability and the psychological burden of passengers in the surrounding vehicles are optimizing target.The trajectory planning model for vehicle LC under the obstacle-free scenarios is established,by solving this model,the optimal trajectory that meets the requirements of LC constrains in the surrounding environment is obtained.The optimal trajectory under these conditions provides the premise for trajectory selection of vehicles’ cooperative LC.Secondly,based on the planning LC trajectory of vehicles in the obstacle-free scenarios,the conflict scenarios of vehicle LC are established,the coordination criteria for high-priority vehicles and low-priority vehicles are formulated,and cooperative LC strategies for the single vehicle and two-car groups are proposed,these strategies meet the spatial and temporal constraints.The trajectory deviation index is constructed to evaluated the closeness between all feasible LC strategies and the optimal LC trajectories.This index is used to figure out the feasible LC trajectory closest to the optimal trajectory under different working conditions.Finally,the vehicle dynamics model and the magic formula tire model are constructed,and the dynamic simulation of the adjustment strategy for cooperative LC is verified.Through the joint simulation of CarSim and Simulink,the vehicle’s status under low-speed(5m/s),medium-speed(15m/s)and high-speed(33m/s)driving conditions is compared and analyzed.The results show that the trajectory planning strategy and the trajectory tracking control method of this study satisfy the control performance requirements.The actual output trajectory obtained by the dynamics simulation is consistent with the theoretical expected trajectory calculated by the proposed model.The corresponding adjustment strategy is as following:In the conflict scenarios,the low-priority vehicles are selected for lateral trajectory adjustment.If the condition of the low-priority vehicles are not satisfied in the actual working condition,then the high-priority vehicles under the low-speed and medium-speed driving conditions are selected for longitudinal trajectory adjustment.Under high-speed driving conditions,the longitudinal trajectories of the both are selected for adjustment simultaneously. |
