Study On The Automobile Automatic Steering Mechanism And Its Control System

Automatic steering system is a important part to realize the intelligent cars and the driverless cars.The key of the system’s mechanism design is to integrate a set of double planetary wheel drive mechanism which make steering wheel,steering mechanism and executive steering motor be connected to each other,so as to realize the synthesis of the force and movement.For achieving automatic steering and artificially controlled mechanical steering,electromagnetic clutch and electromagnetic safe lock are used to be state switch auxiliary institutions to control the steering system.So when the automatic steering system break down,steering wheel is used to control steering system by driver.This steering system which can realize automatic steering of vehicle as well as keep mechanical connection between steering wheel and steering gear is the current development trend of the steering system.Based on characteristics of the traditionally mechanical steering system,single planetary wheel drive mechanism and double planetary wheel drive mechanism were analyzed and compared,and finally the double planetary wheel drive mechanism which had a public sun gear was chosen to be the synthesis mechanism of the force and movement.Electromagnetic clutch and electromagnetic safe lock were chosen to be state switch auxiliary institutions.Based on mechanical property,the double planetary wheel drive mechanism,the turbine worm transmission mechanism,the jaw electromagnetic clutch and the executive steering motor were designed on parameters and size.Through simplified the components of automatic steering system,the dynamic model of executive steering motor component,under steering shaft component,gear and rack component and steering torque resistance and so on were built.According to the established model of steering torque resistance,the function relation among steering torque resistance with vehicle speed and front wheel steering angle were acquired.So the torque output function of executive steering motor were obtained.A control strategy of front wheel steering angle was determined and a fuzzy adaptive PID controller was designed,at the same time,a return control strategy was determined and a return PID controller was designed.According to the dynamic model of components of automatic steering system,the corresponding simulation models were established for simulation experiment.Experimental results showed that actual output of front wheel angle could rapidly and accurately follow ideal front wheel angle of external input under the premise of guaranteeing car steering stability.The vehicle front wheel could quickly return to zero at the return control mode with return controller.