Research On Reliability And Safety Risk Evaluation Method Of On-board Train Control Center System

The Train Control Center(TCC)is the ground core equipment of the Chinese Train Control System(CTCS).It has functions such as rail circuit coding,control interval signal lighting and so on.However,because the TCC system has a variety of equipments and complicated structure,it has greatly increased the difficulty of reliable operation,equipment maintenance and maintenance of system.In order to improve the maintenance level of the TCC system and improve the subsequent design and reduce the cost of failure,it is of great significance to evaluate the reliability and safety risk of the TCC system.Due to the lack of failure data and the limited epistemic level of the TCC system,it is difficult to obtain accurate system failure mechanism and accurate equipment failure rate.This makes it unavoidable to have epistemic uncertainty in reliability evaluation of system.In the actual operation,the TCC system is affected by environmental factors such as electromagnetic,temperature,and noise,leading to different degrees of performance degradation of various equipment of the system.In other words,the system equipment have several intermediate states in addition to normal operation and complete failure.In addition,during the safety risk assessment of the TCC system,the method of using expert experience to obtain risk data has strong subjective uncertainty.And the single weighting method is often used to calculate the weight of risk factors.This makes the evaluation results less referential.In response to above problems,this thesis has done the following:(1)The reliability evaluation of the TCC system have problems of uncertainty,dynamic failure,common cause failure and recovery mechanism.Based on the analysis of the functional logical relationship of each unit of the TCC system,this thesis puts forward a approach by combining the evidence theory with dynamic Bayesian network.And the Dynamic Evidential Network(DEN)reliability analysis model is established.By using the forward inference ability of DEN,the reliability of the TCC system is obtained by combining the belief measure with plausibility measure of the evidence theory.The effect of common cause failure on system availability is discussed.By using the backward inference ability of DEN,the weaknesses of the TCC system are recognized.Finally,by solving the magnitude of Birnbaum and importance,the influence of basic units with reliability changes and the uncertainty on system reliability are explored.(2)During the actual operation,the equipment of the TCC system will produce performance degradation.In this thesis,multi-state transition model based on Markov is established and introduced into DEN to complete the reliability modeling of the TCC system under multi-state conditions.Compare the influence degree of the TCC system reliability without considering maintenance,considering complete maintenance,and incomplete maintenance.It provides decision support and theoretical basis for improving system reliability and maintenance.(3)The safety risk evaluation results of the TCC system have low reference value.Firstly,failure mode and effects analysis(FMEA)is used to identify the risk factors of the TCC system interface unit.Then,experts are invited to score the risk levels of each failure mode of the interface unit of the TCC system.On this basis,the evidence theory is used to revise the initial evaluation data of experts and eliminate the conflict data.Secondly,the comprehensive weighting method of game theory is used to determine the weight of each risk factor,so as to minimize the information loss caused by individual weighting.Finally,the risk factors of TCC system interface unit are sorted.