The Research About Steering Wheel Position Following Control Based On Automatic Parking

Automatic parking system (APS) will perceive the surrounding environment throughthe sensors installed on the vehicles, and it will reminder driver to take some actionaccordingly, then the system will make the steer wheel follow in accordance withpre-designed control strategies. it can avoid collision to improve parking safety; on the otherhand, it can greatly reduce parking difficulty, it just needs driver controlling accelerator andbrake pedal to improve driving portability. so study on the automatic parking system is veryimportant!the actuator of APS is based on steering system EPS, through controlling steering motor,namely position following control of motor, can make vehicle follow pre-planned path. Inthis paper, three closed-loop control is adopted for motor control, which is made of currentloop, speed loop and position loop. Current loop can limit the maximum motor current toprevent current overshoot, it also can make motor output torque large enough to ensure thestability of the entire system; Speed loop can guarantee a good dynamic following, reducespeed fluctuation, then the system will have a good static stability; Position loop can ensureaccurate motor position or steering wheel position following. When some inside parametersin current loop or speed loop are changed or disturbed, the current feedback and speedfeedback can inhibit them effectively. so the position loop can avoid the influence. Therefore,three-loop control strategy can meet some demands such as without overshoot, strongresistance to load changes and fast response. Establish motor model and control modelaccording to AC asynchronous motor theory, and establish steering model, to achieve unionmotor control simulation.According to the existing automatic parking strategy, Get the ideal relationship betweenthe displacement of the rear axle center and the steering wheel through low-speed vehiclekinematic model, based on that, establish a look-up table.In fact, the velocity of vehicle cannot be constant during parking process, so it will havesome impact on path tracking, in order to compensate the influence generated by velocityfluctuating, this paper will carry out steering wheel following control based on the displacement of the rear axle center, through the look-up table, the desired steering wheelangle can be obtained, then the steering motor will drive the steering system to make thesteering wheel follow the designed. in this process, the actual displacement of the rear axlecenter may has an error, the steering wheel following may has an error, so there will bedouble errors. By simulation, analyze the feasibility of this method.Achieve system in-the-loop simulation test. develop motor controller, build steeringsystem test bench and xPC-Target real-time simulation system to check the followingstrategy mentioned before.