Research On Model-based Fault Diagnosis System For Automotive Electric Power Steering

In today's booming high-speed auto industry,driving safety and comfort are increasingly becoming the focus of the market.Electric Power Steering(EPS)is one of the most important components in modern cars that can significantly improve driving comfort.The functional reliability of the system not only affects driving comfort,but also significantly affects driving safety.Based on this,the fault diagnosis for EPS,not only has great significance for evaluating its working condition,performing sensor arrangement,and achieving fault source acquisition,but also beneficial to the reliable operation of the system and enhancing driving safety.This dissertation based on the National Natural Science Foundation of China“Research on Depth Perception and Human-Machine Cooperative Control of Vehicle Horizontal Driving System”,where the study of fault diagnosis concerning the EPS are discussed,in the paper,we mainly perform fault model establishment,fault mode,effect and critical analysis on the system,the fault detection,isolation and residual generation for fault diagnosis system of EPS is analysed by utilizing the methodology of fault diagnosis based on Structural Analysis(SA).The specific work of this paper are as follows,Firstly,the mathmatical model of EPS is carried out,based on two-degree-of-freedom vehicle dynamics model and two-layer control method,the basic power assist control of electric power steering is completed,and the current tracking of EPS is achieved by using system compensation;then the current and torque tracking are simulated by MATLAB/Simulink,based on the mathematical model of EPS,the fault mode,effect and criticality of the components for EPS are analyzed by introducing the FMECA tools,beside these,the key faults are obtained by qualitative critical matrix,thereby the fault model for EPS is established.Secondly,by introducing the theory of model-based Structural Analysis(SA)for fault diagnosis,graphical MATLAB/GUI structural analysis troubleshooting toolbox was developed,then the structure of the initial electric power steering system fault model system is characterized,so the fault detection and fault isolation are analyzed through Dulmage–Mendelsohn decomposition;furthermore,sensors placement for electric power steering is completed based on SA,Thereby the diagnostic capability of the fault diagnosis system is optimized.Finally,based on SA,the Minmal Structurally Over-determined sets(MSO sets)for fault diagnosis system are obtained,and the sequential residuals are designed for every MSO set,then the Fault Detection and Identification(FDI)system is builed with MATLAB/Simulink,which is compared the fault signal with fixed thresholds,to determine whether the fault occurs or not,the fault detection and diagnosis are completed.To verify the feasibility and availability of fault diagnosis method based on SA for EPS,the residual response results of each set of MSO sets with the theoretical analysis results are compared.