Research On Trajectory Planning And Control Algorithm Of Autonomous Vehicle Expressway Scene

Automatic driving technology plays an important role in improving the traffic environment,improving traffic efficiency,and reducing traffic accidents caused by human factors.However,autonomous driving technology still faces many problems in complex environments,including the trajectory planning and control of vehicles traveling on highways.Therefore,this paper studies the trajectory planning and trajectory tracking control algorithm of autonomous vehicle in the expressway scene.The main research contents are as follows:(1)In order to accurately construct the Frenet coordinate system,this paper designs a reference line smoothing algorithm based on piecewise quintic polynomials.Firstly,the discrete points of the original reference line are segmented and fitted using a quintic polynomial,and then a smooth reference line is obtained using an algorithm based on quadratic optimization.The Matlab simulation verifies that the reference line smoothing algorithm proposed in this paper can obtain high-quality reference lines,and the algorithm has high solving efficiency.(2)Based on the optimized reference line,a Frenet coordinate system is constructed,and a trajectory planning algorithm for lateral and longitudinal decoupling is designed.First,perform path planning,project static obstacles into the SD diagram,use the A * algorithm to solve the rough path,and then construct a quadratic programming model to solve the fine path.Based on the path planning results and the dynamic obstacle trajectory,an ST map is constructed,and a dynamic planning algorithm is used to solve the rough speed.Then,a quadratic programming algorithm is used to solve the final speed curve.The solution results of path and velocity together constitute a complete trajectory,which is transmitted to the downstream tracking control module.(3)In order to track the planned trajectory,this paper designs a trajectory tracking controller based on model predictive control(MPC).A model predictive controller is constructed based on the vehicle model,and a speed tracking controller for the underlying control is designed.Simulation results verify the effectiveness of the trajectory tracking controller proposed in this paper.(4)Joint simulation using Carsim and Matlab/Simulink.In order to validate the planning and control algorithms proposed in this paper,typical operating conditions on highways are designed.The experimental results show that the trajectory planning algorithm proposed in this paper can solve the motion trajectory that meets the safety and comfort of vehicle driving;The trajectory tracking control algorithm can effectively track the planned trajectory and meet the real-time requirements of driving.