Research And Implementation Of Path Planning And Path Tracking Of Parallel Parking System

In recent years,driving a car has become a normal part of life.With the rapid development of automotive electronic technology,people’s demand for assisted driving also increases.Automatic parking technology can not only help people complete the task of parking quickly and safely,but also avoid potential accidents caused by small parking spaces.Aiming at parallel parking,this paper studies the detection method,path planning algorithm and path tracking algorithm of narrow parking space in automatic parking system.Firstly,the simplified model of the test vehicle and the parallel parking environment were analyzed and described.The equivalent angle of the vehicle was solved by using Ackerman steering geometry principle,and then the kinematic model of the vehicle was established to obtain the kinematic equation of the vehicle in the parking process,and the state information equation of the key position of the vehicle in the parking process was given.Secondly,aiming at the environment perception of vehicles in parking system,parking detection algorithm is designed based on the principle of ultrasonic ranging.Aiming at the problem of path planning,an improved method is proposed on the basis of mixed A~* algorithm,including the improvement of cumulative generation value calculation,adding Reeds-Shepp curve to speed up the path search speed,and a method is proposed to exchange the starting point and the target point of the planned path.This method takes into account the influence of obstacle density on the success rate of RS curve search.Reduce invalid nodes and improve planning speed.Simulation results show that the improved algorithm in this paper has good path search effect,strong planning reliability and can realize path planning of narrow parking spaces.The objective function was designed according to the principle of model prediction algorithm,and the path tracking problem was transformed into a numerical optimization problem of quadratic programming.The constraint conditions of the objective function were determined by combining the front wheel angle constraint and the speed constraint of the controlled vehicle,and the path tracker based on MPC(Model Predictive Control)algorithm was designed.Car Sim and Matlab/Simulink were used for co-simulation analysis of the parking space detection algorithm and path tracking algorithm.The simulation results show that the parking space detection algorithm has high detection accuracy and can complete the detection task.The tracking controller can track the path with low speed and continuous limit Angle stably and accurately,which can meet the requirements of the test vehicle’s path tracking control.Finally,the test scheme was designed and the hardware selection was carried out.The electric test vehicle was refitted and the D2 P rapid prototype was selected as the vehicle controller.Based on Moto Hawk module,the steering wheel Angle output algorithm and the working state control program of wheel motor based on ESP assisted motor are designed.Compile the.dbc file to satisfy the communication between the vehicle and the D2 P rapid prototype,burn the built Moto Hawk/Simulink control model into the D2 P rapid prototype through Moto Tune software and complete the real vehicle test.The results show that the automatic parking system in this paper can realize the function of automatic parking.