The Study Of Fault Diagnostic Technology For ABS System Based On Model-based Condtion Monitoring

Automotive anti-lock Braking System(ABS) is the important device that affects the safety of the automobile brake System and driving. The ABS system is capable of shorting Braking distance, improving the direction stability. Whether the ABS system is working properly or not will affects the safety performance of the car directly. In this paper, a mechanical fault diagnosis method based on Matlab/Simulink model was proposed to diagnose the automobile ABS system. The research works provide a certain theoretical basis for mechanical fault prediction and diagnosis of ABS system.Firstly the theory analysis was carried out for the automobile ABS system. And then the working principle, basic structure and control techniques of the ABS system were introduced in details. The control techniques used in the ABS system includes the logic threshold controlling method and the controlling method based on slip ratio. Based on the theoretical analysis, the vehicle dynamics model of single wheel, tire model and slip ratio were built by applying the mathematical modeling method. and corresponding SIMULINK simulation model was established based on mathematical model, Then based on the logic threshold control strategy of the ABS system pressure, the Stateflow control models has been designed to present the process of pressure increasing, holding and decreasing during the ABS working. Finally, the models of uninsured ABS system, ABS system without pressure model and normal ABS system have been established based on SIMULINK control model and simulation. It can be concluded that the normal ABS system to shorten braking distance, improve braking performance plays an important role based on slip ratio,brake pressure and braking distance, the analysis of the simulation curve.Finally, the ABS system common faults have been analyzed, including the wheel speed sensor fault, hydraulic oil leakage fault, hydraulic clamping and plunger pump efficiency loss failure. Four kinds of typical faults of SIMULINK model were simulated based on the ABS control system. The failure occurs simulation curve of brake pressure was obtained. It concluded that the mechanical faults of wheel speed sensors, electromagnetic valves and plunger pump can be detected based on the analysis of the failure curves. Ultimately achieve the goal of fault diagnosis.