Research On Methods And Applications Of Probabilistic Risk Assessment For Low-medium Speed Maglev Train's Maintenance Decision

Maglev train systems are complicated in nature with multi states,failures' dependencies between the components.The conventional combinatorial model can quantify static relationships between logical variables with limited capacity,thus the faults' causes and periodic maintenance's equipment are difficult to be determined.In this paper,probabilistic risk assessment methods used by medium-low speed maglev train's maintenance decision are studied to solve those above problems.Reasonable basis are provided for maglev train's maintenance decisions.The main research contents are elaborated as follows.1.To solve the common cause failure problem of actual systems for maglev train.The implicit and explicit fault tree modeling and probability solving methods are presented.Taking the low-medium speed maglev train levitation control system as an example,the quantitative results of the probability risk assessment are given considering the event correlation failure.The results show that the system failure probability is high by considering common cause failure.2.The applicability of Bayesian Networks is analyzed to deal with multi states system.The transformation algorithms of multi states event tree and multi states fault tree to Bayesian Networks are proposed.Taking the maglev train braking control system as an example,the probability risk analysis model of multi states system based on Bayesian Networks is established.Combined with the results of Bayesian Networks analysis,the potential causes of equipment failure are given,and the system failure caused by the failure of the bottom events is predicted.3.In view of the problem of human judgment's fuzziness.Considering the failure consequences such as personal safety,parking loss,maintenance cost and environmental impact,the combined method of fuzzy analytic hierarchy process and fuzzy comprehensive evaluation is proposed.Finally,maintenance recommendations are given for equipment according to the evaluation results of risk level.4.Combined with the above proposed probabilistic risk assessment methods,the risk based maintenance decision-making system is designed,including the main workflow and database tables.The functions of risk assessment and maintenance decision are realized,which provide the technical support of fault analysis and maintenance decision for train operation and maintenance system.