Research On Key Technologies Of Automatic Parking System

With the improvement of the level of vehicle intelligence,automatic parking has gradually become a hot research field.The automatic parking function not only improves parking convenience and safety,but also has broad application prospects and social value,which can further promote the development of intelligent automobile industry chain.In this paper,the key technologies of automatic parking assistant system are studied.The trajectory planning system,vehicle positioning system and tracking control system are designed to realize the automatic parking function which can meet the safety and reliability.Firstly,the overall design of the automatic parking system with ultrasonic sensors is carried out,and the parking space detection algorithm based on vehicle lateral sensors is validated.Experiments show that the parking system can recognize the exact parking space length by setting compensation parameters when there are errors in parking space edge detection.Secondly,the kinematics model of parking process is established.Considering the vehicle position constraints and collision constraints,the multi-segment parking path based on arc-straight line is planned.By designing simulation experiments under different working conditions,it is proved that the proposed algorithm can achieve effective parking path planning.Furthermore,in order to ensure the accuracy of track tracking control in parking process,vehicle positioning method based on wheel speed sensor is studied.By designing Kalman filter to filter wheel speed noise and using least square method to estimate the correction coefficient of wheel rolling radius,more accurate wheel speed information can be obtained,so that the maximum error of vehicle position can be controlled within 1%,which provides more accurate position feedback information for tracking control system.In this paper,a data storage method based on trajectory characteristic parameters is proposed.A preview PID control system with trajectory lateral distance error as input variable and steering wheel angle signal as output variable is designed to track and control the vehicle.The simulation results show that the proposed control strategy is feasible.To verify the performance of the automatic parking system,based on the dSPACE rapid control prototype,the overall framework of the test prototype with perception function,decision-making function and human-computer interaction function is built,and tested by designing several groups of different parking space sizes and different parking directions.The test results show that when the parking space size is moderate and the parking process meets the relevant technical indicators,both the left parking space and the right parking space can achieve parallel parking and vertical parking.