Research On Basic Event Ordering Methods Of Binary Decision Diagram Base On Structural Importance

Fault tree analysis(FTA)is an effective method for reliability analysis and fault diagnosis.Binary decision diagram(BDD)is an effective technique for fault tree analysis and quantitative analysis.In the transformation process of fault tree to BDD,the key is to sort the basic events,for the order of basic events make a direct impact on the size of BDD.The larger the size of BDD is,the more the redundant cut sets will get,which can affect the efficiency of the fault tree analysis.Considering the impact of several factors on BDD scale,such as the layer of basic events in the fault tree,an ordering method of basic events based on structural importance is proposed in this thesis.A priority strategy including five priorities is used to order the basic events,and the five priorities are the layer of basic events in the fault tree,the repeated times of basic events,the next location of repeated events,the logical gate type of the parent node and the order of top-down and left-right.In this thesis,the proposed method is verified by experiments.The experimental results show that in the most of the selected fault tree datasets,compared with the other two algorithms,the proposed algorithm has smaller BDD size,less redundant cut sets,and the time of fault tree analysis is shortened.This method can simplify the process of fault tree qualitative and quantitative analysis,and improve the efficiency of the fault tree analysis.Finally,according to the proposed basic event ordering algorithm,the thesis designs a FTA system.