Research On Electromotor Matching Analysis And Control Algorithm For Steer-by-Wire System Of Light Vehicle

Steering-By-Wire System (SBW) combines Machinery Manufacturing Technology with electronic information technology, cancells mechanical linkage between the steering wheel and the front wheels. we can design the steering characteristics,change the road feeling and the reactive Performance.The advantages of SBW is more obvious than traditional steering system.it adapts to the trand of Technology's development ,it's the research direction of steering system.The thesis focuses on the control algorithm and simulation of SBW and electromotor,it also pays attention to the building of the hardwire-in-the-loop test bench. The following is mainly content in the thesis:Chapter one introduces the function and development history of steering system,describes the present status, Structure,principle,advantages and the questions needed to solve of the SBW.Chapter two,I constitute a mathematic model of SBW system by Matlab/Simulink software according to reduced order theory and complete methods of modeling.The thesis also constitutes a 8-DOF vehicle model which contains tire model, reactive torque modle and other assistant models.All these modles establish a foundation for testing the control algorithms of SBW and electromotor.Chapter three,BLDC is used in the design of SBW as a electromotor which is developed, easy to control and has small size. The thesis builds BLDC mathematic modle,analyses the principle of motor and research how the motor to change speed. This thesis also uses more accurate double closed loops theory to control the motor and determine the control parameters with PID control method. Finally, a simulation is made to test the BLDC mathmatic modle.Chapter four, This thesis analyse the SBW control algorithm.The control algorithm in SBW is devided to two parts:Steering wheel reactive control for road feeling of driver and the steering executing system control based on stability of automobile.In the steering executing system control algorithm.first of all, The thesis researchs how to control the steering executing electromotor,uses target current and actual current to determine the target speed through PID controller,then uses the double closed loops of motorself to make the eletromotor work,finally realizes the target front wheel angle.Secondly, this thesis studies the ideal steering ratio from which I study the front wheel angle control algorithm.The simulation experiments prove that in the steady steering the ideal steering ratio can make the car become neutral steering. The thesis also use yawrate feed control based on ideal steering ratio to control target front wheel angle with ideal yawrate. some simulations about front wheel angle prove that yawrate feek is much effective than only use ideal steering ratio.In the control of steering wheel reactive system, this thesis analyses the reactive torque on steer wheel in different driving status. The thesis uses dynamic modeling to determine the target reactive torque and studies the control algorithm through electromotor model.Reactive control consider changing the damping coefficient of steering wheel system to change the rate and vibration of returning to midpoint.Chapter five,the hardwire-in-the-loop test bench for the steer-by-wire system is a good way to test control algorithm,the performance of electromotor and different Sensor.Before the real car experiment,it's neecessary to build a test bench.This thesis studies the design of SBW test bench program. The thesis use Magnetic Partical Brake in the loading resistance system. This thesis discusses the matching analysis of main parts in SBW system and uses these ways to determine the models of different part.It also introduces the principle and structure of signal transmission and control sysytem.Chapter six, The thesis uses steering wheel system and XPC system to make a series of experiments,test the performance of electromotor and sensors. The thesis also makes reactive torque control and reactive control experiments with mathmatic model.Above all,this thesis builds SBW dynamic simulation model and BLDC model through Matlab software,studies how to control electromotor speed and control algorithm . The thesis builds the hardwire-in-the-loop test bench for the steer-by-wire system and makes the performance experiments with this bench.