Research On Vehicle Vertical Parking Path Planning And Motion Control

As the increase of car ownership,urban parking spaces have become increasingly scarce.So the size of parking spaces has been designed to be smaller and smaller.Nowadays parking has become a major problem when traveling.The automatic parking system has become a research hotspot due to frequent traffic accidents caused by parking errors.Most of the research literature on existing parking systems ignore initial course angle of and steering constraints of the vehicle,which will lead to a discontinuous curvature of the planned reference path,thereby affecting path tracking.In order to address this issue,this paper proposes a path planning method that satisfies the initial heading angle and motion constraints of the vehicle,and a vehicle motion control strategy that combines feedforward and feedback.The main content of this thesis is as follows.(1)The principle of parking space detection is introduced.The vehicle and parking environment are simplified.The kinematics equation of vehicle is derived according to the vehicle motion relation.The position estimation is performed based on the vehicle wheel speed pulse signals.The feasibility of the kinematics model and the position estimation algorithm is verified by simulation.(2)Parking path plan is introduced in this section,the size of the parking space and obstacle constraints are determined in the vertical parking process.A feasible path is planned according to the geometric method.In order to improve the feasibility of the path and solve the problem of steering curvature constraint,the path is optimized by using a quadratic spline function to obtain a path with continuous curvature and satisfying the vehicle steering constraint.Off-line simulation was performed by Matlab.The simulation results show that the generated path satisfies obstacle constraints and vehicle steering constraints.(3)Parking motion control is introduced in this section.Parking decoupling method is adopted to divide the vehicle motion control into longitudinal control and lateral control.The control strategy of preview error feedforward and heading angle feedback is adopted in the horizontal control.And the classical PID control strategy is used in the vertical control.A vertical parking joint simulation platform is established by Carsim / Simulink.The simulation results show that the vehicle tracking effect is good,the system response is fast,and the stability is high.(4)In order to verify the feasibility of the entire vertical parking algorithm,a real vehicle experimental platform was set up to verify the algorithm.The standard C language code of the target chip was generated by using Simulink code,and it was compiled and burned into the controller.Experiments were performed on different initial heading angles.The feasibility of the parking control algorithm in practical application is verified by analyzing the results of simulation and experiment.