A COMPONENT BEHAVIORAL-MODEL FOR AUTOMATIC FAULT-TREE CONSTRUCTION

Abstract

This study presents a new definition of events, an extended decision table, a virtual transfer component, and two pruning procedures for use in systematically constructing fault trees. The component states are modelled by events, which are defined by both qualitative event descriptions and quantitative event types. The quantitative event types are proposed to clarify the vagueness inherent in qualitative event descriptions. Moreover, decision tables, which are employed in the literature to model the behaviour of components, are extended in this study to generate succinct fault trees. A virtual transfer component is defined to deal with redundancy, such as k-out-of-n and standby modules. The construction of fault trees begins with the TOP event and traces backward to the primary and undeveloped events of components based on the structural configuration of the system and extended decision tables stored in a database. Procedures for producing transfer symbols and combining successive logic gates with gates of the same type are proposed to prune the generated fault tree during and after the tracing process, thereby reducing the construction time and the amount of computer memory needed. A hydraulic brake system and a pressure tank system are employed as examples to demonstrate the proposed method. The results of the examples show that the proposed method efficiently generates succinct fault trees for systems with redundancy.