Research On The Safety Risk Assessment Of Radio Block Center

As a core ground subsystem in Chinese train control system at level 3(CTCS-3), radio block center is a vital equipment to ensure safe operation of the high speed train. Radio block center is a railway signal control system based on a computing platform which guides failure to safe side, so traditional safety methods based on the technical rules and regulations can no longer fulfill safety requirements of signal system. In order to manage the radio block center more scientifically, a complete theory of risk assessment can be adopted to evaluate the risk of system in the design phase. In this thesis, the correlation functions and interface modules of the radio block center are selected as the research object which has been studied in the risk assessment.As for radio block center, its historical risk data are relatively less and it is difficult to gain the effective data. Primarily, risk assessment needs a large of historical risk data. In addition, as a high reliability device, radio block center has a shorter operational life and deficient risk data. Thus, it is impossible to do the evaluation completely based on the statistical data. In this case, the system risk level evaluation based on expert experience is needed. And the expert scoring data management based on evidence theory is necessary to make the assessment more objective and reasonable.Risk identification is the first step in the process of the system risk assessment. Failure mode and effect analysis(FMEA), hazard and operability analysis(HAZOP) are used to identify and summarize the failure mode of the functions and interface modules for radio block center. Then, through summarizing and analyzing the failure causes and failure effects, the corresponding risk identification tables can be achieved. Risk identification results show that the combination of FMEA and HAZOP can identify the key failure mode and analyze the weak point in the design of radio block center.Secondly, a scientific method of risk analysis is necessary. By the combination of expert experience and spot investigation, the relative importance and risk rating score of each function and interface modules are operated based on the standards of risk assessment. Taking the function of temporary speed restriction as an example, analytical hierarchy process is applied to obtain the weight matrix by dealing with the weighted data. Besides, the fuzzy evidence theory and the cloud discount evidence theory are respectively applied to convert the investigation data into corresponding matrix of the basic probability assignments(BPA) function. Then the result of risk analysis can be determined by combining the weight and function matrix. Risk analysis results show that evidence theory is suitable for the risk assessment of railway signal system based on expert knowledge, fuzzy evidence theory analytic can effectively reduced the subjective factors of the assessment results of experts, and cloud discount evidence theory can reflect the uncertainty such as randomness and fuzziness of the risk analysis, and solve the problem as incomplete knowledge.Finally, on the basis of the results of the risk analysis of each function and interface modules, the corresponding improvement measures and suggestions are put forward for the radio block center, and the assessment results can provide reference for the designers to improve the system design and foundation for maintenance personnel to draw up maintenance plans.