Model Free Adaptive Control Based Automatic Car Parking Systems

ABSTRACT:For the automatic parking system, schemes about the three stages of automatic parking which are parking space detecting, path planning and path tracking scheme are given, then analyses the characteristics of the kinematics model of a four-wheel car, and gives the control target of the automatic parking system. Based on the proposed control target and considering the situation of parking under constant car speed, automatic parking under constant speed based on prototype model free adaptive control (MFAC) scheme is proposed. To solve the defects of the above scheme on exciting steady state error of trajectory tracking when parking, this paper further proposes the compensation algorithm for the target orientation angle of the car based on real time coordinates. Automatic parking under constant speed based on MFAC scheme with coordinates compensation is the integration between the compensation algorithm and the automatic parking under constant speed based on prototype MFAC scheme. On the basis of constant speed parking, considering the speed as one of the control variables, automatic parking under variable speed based on prototype MFAC scheme and automatic parking under variable speed based on MFAC scheme with coordinates compensation are proposed.In order to verify the effectiveness and superiority of the proposed schemes, variable speed automatic parking and constant speed automatic parking MATLAB simulation on two types of cars are given. In order to verify the adaptability for different speed and different types of cars and the superiority relative to the traditional PID algorithm of proposed schemes, the constant speed automatic parking simulation is about a contrast experiment among the automatic parking under constant speed based on prototype MFAC scheme, the automatic parking under constant speed based on MFAC scheme with coordinates compensation and PID algorithm under two constant parking speeds. The automatic parking system under variable speed is an MISO (multiple input single output) system which adopts the car speed and the front wheel angle as the system inputs, and adopts the orientation of the car as output, and the simulation of the automatic parking under variable speed is to verify the effectiveness of the automatic parking under variable speed based on prototype MFAC scheme and the automatic parking under variable speed based on MFAC scheme with coordinates compensation.The simulation results of automatic parking under constant speed show that the automatic parking under constant speed based on prototype MFAC scheme and the automatic parking under constant speed based on MFAC scheme with coordinates compensation can both adaptive the automatic parking process on different types of cars under different speed, and these two schemes have smaller tracking errors than PID algorithm. For the addition of the compensation algorithm for the target orientation angle of the car based on real time coordinates, the automatic parking under constant speed based on MFAC scheme with coordinates compensation has higher tracking precision than the automatic parking under constant speed based on prototype MFAC scheme. The simulation results of the automatic parking under variable speed show that the automatic parking under variable speed based on prototype MFAC scheme and the automatic parking under variable speed based on MFAC scheme with coordinates compensation can both complete the automatic parking process on different types of cars. The simulation results of the automatic parking under constant speed and the automatic parking under variable speed verify the effectiveness of the proposed schemes in this paper, and the proposed schemes has smaller tracking errors than the traditional PID algorithm on x axis, y axis and the orientation angle of the car. The proposed schemes have great superiority, which laid a foundation for practical application.