一种多阶段任务系统的BDD排序新方法

A Novel Binary Decision Diagram Variable Ordering Approach on Phased Mission System

近年来,BDD(二元决策图)的分析方法越来越多地被用于多阶段任务系统可靠性分析中。BDD方法应用的一个关键是在从故障树向BDD转换时需要对底事件进行排序,所选择的排序顺序将影响构造的BDD的节点数。与单一阶段任务系统相比,多阶段任务系统的可靠性分析由于阶段之间的相关性而变得更加复杂,将一般的BDD排序方法直接应用于多阶段任务系统的BDD分析很难得到令人满意大小的BDD。在考虑多阶段任务系统的结构和特性的基础上,通过共同失效组件对多阶段故障树化简,提出了基于最小相邻组件优先相邻排序的多阶段任务系统BDD排序方法。通过与一般的排序方法相比较,这种新方法可以生成更理想的BDD结构。

In recent years,the BDD （Binary Decision Diagram） approach has been widely used for phased mission system （PMS） reliability analysis. To successfully use BDD technique,a key issue is the variables ordering while converting the fault tree into BDD format. This will impact the finalized BDD size. Compared with the single phase system,the phased mission system is more complex due to the independency between its phases. So it may be not suitable if using the exsited BDD variable ordering approaches for PMS-BDD construction. A new PMS BDD variable ordering method is proposed in this paper. Considering the structure and charateristic of PMS,this new method emphsizes the adjacence of neighbor variables＇ ordering and simplifies the BDD construction process through common failure components reduction. An example given in the end manifests the advantage of this new method.