Research On Multi-stage Parallel Parking Based On Clothoid Curve

With the progress of the times and the development of science and technology,the automobile industry is facing the wave of "new four modernizations".In the course of daily use of cars,many drivers have been troubled by the reverse storage.With the increase of car ownership year by year,the problem of "difficult parking" is becoming more and more significant.As an important product in the field of intelligent driving,automatic parking system arises at the historic moment.In this paper,the decision planning and motion control of parallel parking condition in the automatic parking system are studied,and the feasible parking path is planned based on the vehicle motion characteristics,and the vehicle motion controller is designed to track the parking path.Firstly,the vehicle kinematics model is established by theoretical research on vehicle kinematics characteristics.Combined with Ackermann steering principle,the internal logic of vehicle motion law and clothoid curve is deduced.By analyzing the relationship between the position and pose information of vehicle motion and the mathematical model of the cyclotron,an iterative method of calculating the vehicle position and pose information is proposed to calculate the parking path of the cyclotron,and then the parking path that the vehicle can follow stably is planned.Secondly,the model predictive control of vehicle lateral control strategy is introduced in theory,and a model predictive control method based on the reference path point optimization is proposed to solve the problem of the error accumulation caused by the non-integrity constraints of vehicle movement in the actual tracking process.Through the simulation experiment of reference path tracking in Matlab/Simulink,it is verified that the lateral control strategy proposed in this paper can better meet the real-time and stability requirements in the process of parking path tracking.At the same time,the vehicle longitudinal control model has great uncertainty,so the PID error feedback regulation control method is adopted to keep the speed in a stable state in the process of single-step parallel parking.Finally,the vehicle motion control strategy model is established in Matab/Simulink,and the tracking simulation experiments of the multi-stage parking path based on cyclotron curve and arc straight three-stage parking path proposed in this paper are carried out on the basis of vehicle kinematics model.Through the analysis of the simulation experimental data,it is verified that the circular multi-section parking path proposed in this paper has better tracking performance.In order to further verify the feasibility of the parking path,the vehicle dynamics model was established in Car Sim,and the tracking simulation experiment of the parking path was carried out through Simulink/CARSIM co-simulation.The parking path designed in this paper is simulated by LEGO＿EV3 controller on LEGO smart car to verify the feasibility of the parking path.