Modeling And Co-simulation Analysis Of Automotive Electric Power Steering System

With the rapid development of China's national economy and science and technology,people's living standards continue to improve.As an alternative tool,the car's popularity is increasing year by year.People also pay more and more attention to the ride comfort,handling stability and driving safety of the car.As an important part of the car structure,the steering system is also very necessary for systematic research.After years of iterative development,the automotive steering system has gradually developed from the original mechanical system to the elevtric power system which is now widely used Steering,(hereinafter referred to as EPS),compared with other steering systems,EPS system can provide corresponding assistance according to different driving conditions of the vehicle,so as to better handle the relationship between steering portability and road sense.Firstly,the structure and working principle of EPS are analyzed systematically.According to the dynamic law,the mathematical models of steering wheel,steering input shaft,torque sensor and steering output shaft are established respectively,and the corresponding simulation model is built in Matlab/Simulink.Secondly,the permanent magnet synchronous motor with simple structure and strong reliability is selected as the power motor of EPS system.At the same time,the working principle of the permanent magnet synchronous motor is explored,the mathematical model of the permanent magnet synchronous motor in different coordinate systems is analyzed,and the direct torque control with fast response and strong anti-interference ability is used as the driving algorithm of the motor,which is established in Matlab/Simulink software The simulation model of the motor is established,and the validity of the model is verified by the torque and speed simulation experiments.Thirdly,the upper control strategy of EPS system is studied,and the basic assistant control strategy is taken as the key research object.Based on the analysis of the characteristics of three kinds of typical power assisted characteristic curves:straight line,curved line and broken line,the linear curve with relatively simple structure and easy to design is selected for design,and the parameters of the curve are determined by relevant equations.Finally,this paper analyzes the composition of the whole vehicle model,sets up the size parameters of the car body,the tire parameters and the suspension parameters in the CarSim software,builds the whole vehicle simulation model,through the data interaction between the CarSim software and MATLAB/Simulink software,establishes the joint simulation environment,and carries out the Steering transient response simulation experiment and steering portability simulation experiment.