Research On Path Planning And Tracking Control Of Automatic Parking System Based On Preview Model

With the progress of society and the improvement of people’s consumption level,the popularity of cars is also getting higher and higher,and the problem of parking is becoming more and more obvious.Especially in the city,due to the narrow road and limited parking space,some novices often dare not to park in the small parking space,or worry about the car scraping during the parking process,which has brought great distress to many car owners.In order to solve these problems,different automatic parking assistant systems have been developed by universities and research institutions.By comparing the advantages and disadvantages of various parking systems,this paper designs a simple and effective parking system for vertical parking and parallel parking.First of all,this paper uses ultrasonic radar to detect parking spaces.This paper introduces the ranging principle and logic algorithm of ultrasonic radar,designs three common parking conditions of vertical parking and parallel parking,and verifies the effectiveness of the method through Simulink and Pre Scan joint simulation.Secondly,in the aspect of path planning,this paper first establishes a vehicle kinematic model based on Ackerman steering principle;then,through the geometric constraints of parking space and surrounding environment,the basic paths of vertical parking and parallel parking are designed,and the initial parking area is obtained.In order to get the path with continuous curvature,this paper uses polynomial fitting and steering wheel angle two different methods to optimize the path,and through MATLAB simulation comparison.By comparing the initial area width,space utilization,path curvature change,final displacement deviation and heading angle deviation of the two methods,the advantages and disadvantages of the two methods can be obtained.Finally,in the aspect of tracking control,this paper designs PID controller based on preview model.For the steering wheel angle optimization of vertical parking and parallel parking,the feedforward control is also introduced.Through Simulink and Pre Scan carry out the joint simulation of multiple working conditions,to compare the tracking displacement error and heading angle error of basic path,polynomial optimization path and steering wheel angle optimization path.The simulation result shows the tracking error of the steering wheel angle optimization path is the smallest and the tracking effect is the best.Furthermore,the validity of the steering wheel angle optimization method is verified by the real vehicle test.