| Railway time synchronization network is an important part of bearer network. The network provides a unified standard time information for railway in order to ensure the safety of train operation and the accurateness of fault location.Rliability research of the network is very important to improve the system and lay down the repair strategy. With railway time synchronization network selected as the object of research, the evaluation of the reliability of the system and the influence of many factors on the system reliability are studied through modeling with Bayesian and Petri to evaluate the reliability.Railway time synchronization network is a network that features complex structure and key redundant equipments. For the conventional reliability analysis methods, such as the reliability block diagram, fault tree and Markov process, there are some deficiencies in the analysis of its equipment reliability. Due to the reliability assessment needs a plenty of data,and the network is under construction and the risk data are incompleted, the estimation of equipment reliability based on expert knowledge and experience is needed. However expert scoring method is difficult to ensure the objectivity and accuracy of evaluation results, so the fuzzy bayesian method is applied in dealing with the results of expert scoring respectively by combing the fuzziness and randomness, which can make the evaluation more scientific and reasonable. Therefor, the fuzzy theory is employed to evaluate equipment reliability of the railway time synchronization network in the thesis. First of all, failure modes effects analysis(FMEA) method is used to identify the risk of the functions for the railway time synchronization network. By combing with the expert experience and spot investigation, and the common cause failure is analized. Secondly, the bayesian model is established based on fault tree model. Finally, the thesis analysis the reliability of railway time synchronization network is analized through causal reasoning and diagnostic reasoning algorithm in the thesis.Equipment reliability assessment results show that the railway time synchronization network’s reliability can meet the requirements, FMEA method can identify key projects and analyze the weak points of railway time synchronization network, fuzzy bayesian analytic can effectively reduced the subjective factors contained in the results of the assessment of experts,and it is suitable for network evaluation.As the conventional reliability analysis methods is not good at analysis network performance, the stochastic petri net is used to evaluate the functional reliability of railway time synchronization network in the thesis. Firstly, the communication model based on optical fiber delay, optical fiber fault, electromagnetic interference and information check is established.Secondly, the synchronous model is established based on communication model and time transmission scheme. Finally, the equipment reliability of the railway time synchronizationnetwork is assessed through stochastic Petri net. Functional reliability assessment results show that the railway time synchronization network has a high success rate of synchronization, and the stochastic Petri net method is suitable for dynamic analysis on the network performance. |
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