Analysis of leakage fault characteristics of air control valves in train braking system

In order to monitor and warn the leakage fault of air control valves in train braking system, rapid analysis of fault characteristics is the key premise. The relay valve used in train braking system was taken as an example in this paper. Its working principle and physical structure were clarified, and the leakage fault was divided into internal leakage and external leakage based on the airflow direction. The simulation model of relay valve was established, and the internal and external leakage faults were simulated by using the model-based fault injection method. The influence laws of leakage faults on the output pressure and balance state of the relay valve were analyzed, and it was found that the relay valve had a dynamic balance position besides the tri-state position. Finally, the leakage simulation bench test was carried out, and the test results show that the relay valve model could correctly analyze the leakage fault characteristics, and the output pressure could be used as the fault characteristic to warn leakage faults. The method proposed in this paper provides an effective way to analyze the fault characteristics of braking system and can be used to obtain fault data for fault diagnosis.