COMPUTER-AIDED FAULT TREE SYNTHESIS .2. FAULT TREE CONSTRUCTION

This paper is Part II of a series devoted to fault tree synthesis. Part I started with the introduction of component models that showed all fault propagation through the components and fault initiation by the components in both directions (upstream and downstream). Subsequently, it was shown how to create system models that interconnect a system's components and environmental variables. A fault tree construction algorithm was then introduced which was able to generate fault trees from the given system and component models in two steps. First, a causal tree was constructed showing the propagation paths for all basic events leading to any deviation in the top parameter. All control loops (feedback and feedforward loops) in this causal tree had to be traced prior to any fault tree construction since they might have prevented some faults from reaching the top parameter. They consequently required a special treatment. Part I ended showing how to adapt the causal trees for these loops. Part II discusses the final step of the fault tree construction algorithm, i.e. it shows how fault trees can be abstracted from the causal diagram, and ends with a comprehensive example. Finally, Part III will discuss a method for real-time fault location, which is based on the causal tree construction procedure introduced in Part I.