Fault diagnosis of simplified fault trees using state transition diagrams

The fault tree (FT) is a well-established and well-understood technique for reliability assessment and fault analysis in the aerospace field. Recently, some researches combine FTs with other technologies to optimize the fault analysis process, but there are still some issues. One issue is that some ignored logical contradictions generate unreachable subtrees in the process of building FTs. Another is that when performing fault diagnosis, some studies only focus on the basic events or treat the basic events and intermediate events equally, which results in some special situations not being considered. To tackle the above two issues, we propose a new methodology for simplifying the FT and then performing fault diagnosis. By transforming the FT into a state transition diagram (STD), we perform satisfiability analysis on unreachable subtrees to simplify the FT. Then when performing fault diagnosis, we use the transformed STD to handle basic events and intermediate events separately. This can reduce unnecessary operations and identify multiple failure combinations. Finally, we use a case to demonstrate the effectiveness of our proposed methodology.