Research On Safety Analysis Method Based On Safety Risk State

Safety analysis is the process to use the safety risk information which can be gotduring the operation of the system to assess its safety. Nowdays, there are many safetyanalysis method, but none of these methods can carry out the analysis based on thesystem state space. So, the thesis puts up a safety analysis method based on safety riskstate. At first, we give the description of the system safety risk and define the safety riskstate, critical state and crucial component. According to the definition, the identificationmethod of safety risk critical state and crucial component and the analysis method ofsafety risk failure sequence are presentes. Afterwards, the thesis estabilishes the modelof safety risk state transition and estimates the safety risk state and its transition time.Considering that most of the systems can get the performance degradation data whichreflects its safety risk, the estimated method of system safety risk level based onperformance degradation data are researched. And then, the thesis puts up the controlmeasure of safety risk level based on the safety risk importance when the safety risklevel is incompetent. The main achievements are as follows:(1) A description method of safety risk and safety risk state is presented.The description of safety risk is discussed, including the consequence severity andprobability. Then from the perspective of state space, the system state, safety risk stateand the corresponding critical state and crucial components which characterize theboundaries between various safety risk states are defined respectively and the exampleis given. The safety risk state can describes the system safety risk clearly and explicitly,and the description method can ravel the importance of the operation monitoring. Allthe above provides the theory basis.(2) The identification method of safety risk critical states is advances.After the analysis of the hazards and its influence of system, the thesis puts up theidentification method of safety risk critical states based on Petri Net. And then, thereachability graph which characterizes the reachable system states including normalstate, low risk state, middle risk state and high risk state and the transition pathesbetween the states is achieved through the simulation of Petri Net. Afterwards, we canidentify the safety risk critical states based on reachability graph. The Petri Net modelof the identification of safety risk critical states can characterized the complicated logicrelation such as “and”,“or”,“concurrence”,“confliction”, and it can identify the safetyrisk critical states through the reachability graph analysis. The method of the thesis issignificant for safety risk control.(3) An analysis method of safety risk state transition process integrated withmulti-information is brought forward.To solve the problem of analysis of safety risk state transition process, the thesis advances an analysis method that fuses various safety risk information. First, the safetyrisk state transition process is described and the corresponding model is established.Then the particle filter and Markov process are utilized to analyse the transition processbased on the fusion of various monitored data, and the transition time between safetyrisk states is estimated based on the monitoring result. Finally, the model accuracy isanalyzed using bootstrap method. The analysis result reveals the vital significance ofsafety risk state transition analysis to the prevention and control of accident.(4) A safety risk level analysis method based on the performance degradation isput forward.Most of the systems can get the performance degradation data which reflects itssafety risk. so, for the purpose of the safety risk level estimation with performancedegradation data, the estimated method of system safety risk level based onperformance degradation data are advanced. After a state reliability modeling methodbased on performance degradation of the components is proposed, the safety risk modelof system is constructed and the processing method of input information is discussed.Then the safety risk level is determined based on the given evaluation criteria andcalculated probability of each possible safety risk state, and “the probability ofdiscarding right consequences” and “the probability of accepting wrong consequences”are evaluated using the bootstrap method. After the safety risk importance is defined,the system safety risk control method based on the safety risk importance is proposed.