The Study Of Fault Diagnoiss For Air Brake Systems Based On Model

The performance of the air brake systems for the passenger car will influence the safety during the traveling and the reliability of the parking directly, and it is the main reason of accidents. Leaks and out of adjustment of the push rod stroke are the two prominent faults in the air brake systems. The response of the brake system will be slower, the braking force will be lower and the braking distance will be increase in the presence of leaks. These problems will easy to causing traffic accidents. Out of adjustment of the push rod stroke will result in the loss of brake force. This paper study the method for diagnosing the fault in air brake systems by establishing the mathematical model for the air brake system and conducting the brake tests on the brake simulation bench. The main research contents of this article including:(1) This paper focuses on the air brake systems for the passenger car and builds the mathematical model by analyzing the structure, principle and the working condition of the key brake components. The model was built under the consideration that there is no fault in the air brake systems. We modeling the air brake systems in terms of solving mass flow rate, and analyzing the force balance, after that, we have model the leak-free pressure dynamic model of air brake system and the push rod stroke estimation model.(2)The demand of the traveling brake simulation tests was proposed by analysing the structure and the working principle for the air brake system. A vehicle air brake system simulation test bench was designed according to the demand. We have design and conducted the selection of design for the hardware parts of the test bench.(3) In the Lab VIEW software programming environment, the software test systems for the brake simulation test were designed and adopt the designing thought of modularization. The software test systems have achieved the following functions: the control of force load, data collection, data storage and process monitoring.(4)A leak fault diagnosis method based on the model for the air brake systems was proposed. The model is on the basis of theoretical analysis and experimental data processing. For a given brake application, the governing equations of the model will be solved numerically to obtain the solution for the brake chamber pressure. This will be compared with the experimental data. The threshold value for judging the leak fault in the air brake system was given. The push rod stroke during the braking was estimated by the push rod stroke estimation model. The estimated push rod stroke was detected whether within the effective range to judging out of adjustment fault in the brake system.