Research On Automatic Parking Trajectory Planning And Tracking Control Strategy

Along with the development of science and technology,automobile driverless technology is gradually mature.As an important puzzle of driverless,automatic parking technology has become the focus of domestic and foreign scholars and automobile enterprises.This paper explores the current research at home and abroad,analyzing the status of automatic parking trajectory planning and tracking control strategy,this paper chooses trajectory planning and tracking control strategy as the research direction.Based on the analysis and comparison of the existing automatic parking trajectory planning methods,the minimum radius backward push planning method is designed as the parallel parking planning method.Considering that the parking space is not enough,the collision avoidance constraints in the parking process are added to divide the parking starting area,and the vertical parking trajectory planning method combining single step parking and multi-step parking is designed In order to ensure the success rate of parking planning,the single step parking planning method with high efficiency is adopted when parking space is abundant,and the multi-step parking planning method is adopted when parking space is narrow.Trajectory tracking control for the automatic parking system is studied using kinematics model,this paper adopts two degree of freedom dynamic model as the research object,analyses the automatic parking motion process,through the Ackerman steering geometry principle,will be around to different round corner is simplified to bicycle front wheel angle to the equivalent of the model.Then to design the automatic parking path tracking control strategy,using speed longitudinal cascade PID and the PID position controller to control the vehicle’s longitudinal motion,and by using Simulink to build the longitudinal tracking controller model,with four kinds of condition of longitudinal tracking controller for validation.Based on LQR horizontal tracking controller based on optimal theory,adding feedforward control constitute the optimal feed-forward LQR controller as a horizontal tracking controller to control the lateral movement of the vehicle,using Simulink model,set up horizontal tracking controller in three relatively harsh desired trajectory curvature change condition,the horizontal tracking controller for validation.Through the analysis of the simulation results,it is concluded that the tracking performance of the transverse and longitudinal tracking controller is better,and the tracking error can be controlled in a small range.Finally,the function of the design of the automatic parking trajectory planning and tracking control strategy is verified.Firstly,a Matlab /Simulink and CarSim co-simulation platform is built.In Simulink,the horizontal and vertical controllers are combined to build a complete trajectory tracking controller.Vehicle parameters and environmental parameters are configured in the CarSim.Secondly,ultrasonic sensors,Raspberry Pi and Arduino are used as the main parts to build an intelligent car test platform,to simulate the performance of the designed tracking control strategy on the real car,and to draw and analyze the data obtained from the test.The results show that the tracking control strategy is effective and feasible in the real car test.