Dynamic Programming And System Control For Multiple-Stage And Parallel Parking Trajectories

As the car has become the people’s subsistence, the research of automatic parking system is becoming a hot topic. This dissertation conducts the depth study of the trajectory of the automatic parking system. On this basis, the estimation of centroidal point speed and the control of the speed of steering wheel are executed. At last simulation and experimental research are executed.The main research and innovation points can be summarized as the following aspects:In this dissertation, considering the fluency of automatic parking process, the vehicle’s parking speed is assumed constant and the parking trajectory equation of the center point of the vehicle’s rear axis while steering wheel rotating uniformly is established. Parking path planning algorithm by many stages is put forward and the quantitative analysis of horizontal ordinate, vertical coordinates and attitude angle of the path are given out; obstacle avoidance conditions while parking are analyzed and the methods to solvie path parameters which can meet obstacle avoidance conditions are obtained; The simulation model of parking trajectory is established, and the smallest parking space is required through the analysis of model, and the trajectory simulation of the whole parking process is carried out.Adjusting strategy of parameters for parking path is put forward and the way of judging parking stage and the computational formula of parking path adjustment parameters are given out, based on the actual situation that the vehicle’s speed is changing constantly in the process of parking. Flow diagrams of calculating new carport and body posture, parking path adjustment parameters are established. The roasting speed of steering wheel and the track of vehicle while parking is simulated by simulation test.Three degrees of vehicle freedom model is established, and parameterized semi-empirical formula of tire is required, based on the need of exact speed and the theory of observer. Longitudinal velocity observer, lateral velocity observer, yaw angle observer are established, and stability and check index of observers are analyzed. The simulation model is built up in veDYNA, and the vehicle speed provided by observer is closed to the speed provided by veDYNA. The real vehicle experiment results show that the error of the observer speed with the actual speed is smaller than others.Based on the difference of the working model of EPS between the parking condition and the normal condition, the steering model of EPS while parking is built up to get the relationship between the torque and speed of motor with angle of steering wheel. The three-loop control of motor and the parameters of PID are researched. The simulation and real vehicle experiment are carried out, and the validity of the control strategy is verified.On the basis of the trajectory adjustment strategy, the speed estimation strategy and the slew control strategy, the hardware system of the whole parking system are designed, and real vehicle test of the whole parking system is conducted, too.