Dynamic Fault Tree Analysis Method

Based on static logic or static failure mechanism,the traditional fault tree analysis is a effective method to analyze system reliability. But it can not be used to analyze the reliability of systems with dynamic randomicity and dependency,such as fault tolerant system,repairable system with redundance (cold spare or hot spare),sequence dependency system and system with spare pool. Markov model can be used to analyze reliability of dynamic system. However,because the size of state space will increasing exponentially as the size of system augments,the construction and solution of Markov model are tedious and error prone,even can not be used. Therefore,it is necessary to study a new fault tree analysis method.Dynamic fault tree exploits the relative advantages of both fault tree and Markov model. Dynamic fault tree is modularized into independent static subtrees and independent dynamic subtrees,then solved by BDD and Markov model separately. This method can improve analysis efficiency greatly if the size of each dynamic subtree is far small relative to that of system.This paper focuses on techniques of dynamic fault tree in system reliability modeling and its qualitative and quantitative analysis. It studies the modularization of dynamic fault tree,presents BDD solution for static subtrees and studies Markov chain solution for dynamic subtree briefly. This paper presents the conversion from dynamic logic gate to Markov chain,the solution of dynamic subtree top event failure probability and the method of obtaining the failure mode of subsystem using Markov model,that is sequence cutsets of the dynamic subtree. The typical approach to importance analysis of component is impractical for large systems in Markov model,so this paper also provides a simple and intuitionistic graph solution based on Markov chain.