Research On Reliability Analysis And Maintenance Decision Of Urban Rail Vehicle Door System

The door system is one of the key factors to ensure the operation of urban rail vehicles safety. The total failure of the door system amounts to above 30% of the total failure of the urban rail vehicles system, which poses a serious threat to the safety of vehicle operation. For this reason, The FMECA and FTA is introduced to make comprehensive analysis for the reliability of the door system, and reliability-centered maintenance is utilized to make repair decision for the door system based on reliability analysis.Firstly, the paper introduces the composition, structure and working principle of the door system, then it analyses the common failure modes and the causes of the fault of the door system.Secondly, the FMECA is used to get the causes, effects and hazard ranking of 12 important failure modes of the door system; then the weighted least squares, the fuzzy weighted geometric average method and fuzzy VIKOR method are introduced to improve FMECA in order to solve the deficiency existing in traditional FMECA analysis. In the paper, the 12 failure modes are applied to verify the two modified methods and the results show that hazard analysis results through the two improved methods can more reflect the actual situation on site.Then, the fault tree of the door system, which sees "the door is not correctly functioning" as the top event, is established to get the minimum cut sets, the top event probability and the bottom events of the fault tree of the important degree; The result shows that EDCU, latching relay and unlock switch S3 are the weak link of the door system.Finally, experienced experts from vehicle maintenance department make logic decision on the door system and its components based on RCM logic decision process then get the best time interval to repair and operate the door system and its components. In order to overcome that people make working time interval decision subjective, the proportional hazard model is introduced to verify the results got by experts on the door system, and the results show that the best operation time interval is 70 days. Therefore, the method of "system maintenance" is used to maintain the door system.