System Failure Analysis Based On BDD Optimization Method

In the field of aerospace,the loss caused by system failure is enormous,so it is very important to accurately evaluate and analyze the reliability of the system.The qualitative analysis of the system fault tree is an important part of the system reliability analysis,which can display the formation mode of the system's failure,identify the weak links of the system,and provide the theoretical basis for the system security design.This paper presents a new method for qualitative analysis of large-scale fault tree and dynamic fault tree and the main contents are as follows:Firstly,SimBDD algorithm is proposed to analyze large-scale fault tree.In consideration of the problem of inefficiency of traditional fault tree analysis and the problem of space explosion while analyzing the large-scale fault tree using BDD method,the SimBDD algorithm based on simplified BDD structure is given in this paper.This paper elaborates the structure of SimBDD,operation method of SimBDD,the method of transforming the fault tree into SimBDD and the way to use SimBDD to find the minimum cut set of the fault tree.In addition,the test of getting the minimal cut sets of multiple large fault trees shows that the algorithm is more efficient to find the MCSs of large fault trees than OpenFTA.Secondly,the hierarchical traversal method is presented to find out the failure path of the fault tree.The problem of space explosion and redundant paths can be produced in the way of splitting the paths.Hierarchical traversal method starts from minimum cut sets and uses hierarchical thought to analyze the fault tree layer by layer,avoiding the problems of space explosion and redundant paths.Third,aiming at the problem of low efficiency of the existing dynamic fault tree analysis method,a dynamic fault tree qualitative analysis method based on SimBDD is proposed.In this method,all the dynamic gates of the fault tree are transformed into a sequential gate expression,and then all the expressions are converted into the way of using the AND gate as the outermost layer by using the transition formula in this article.With the use of timing pairs,the final dynamic fault tree is transformed into static fault tree.With proving the correctness of the conversion rules from sequential formula to timing pairs,the SimBDD method can be used to qualitatively analyze the transformed fault tree.Finally,the SimBDD method and the dynamic fault tree qualitative analysis method based on SimBDD are applied to design the fault analysis software.The software can model the fault of the system,visually display the fault tree and do qualitative analysis of the fault tree.