Method of Computer-Aided Fault Tree Analysis for High-Reliable and Safety Design

Abstract

Fault tree analysis (FTA) is a method of analyzing and visualizing the causes of a fault using a fault tree diagram (FT diagram), which has a tree structure with logical steps. Design engineers developing a new product generally use FTA to analyze many fault events, calculate their probability, and include redundancy systems in the design process. Furthermore, FTA has been used to analyze problems with products and to prevent the occurrence of problems in the design phase. In particular, it is necessary for design engineers to analyze the events after a failure to determine the root causes of the failure of the redundancy systems. However, it is not easy for design engineers to produce an accurate FT diagram in the actual design process. We have developed a computer-aided knowledge management system for creating FT diagrams (FTAid) as part of a collaborative group (The University of Tokyo, National Institute of Advanced Industrial Science and Technology (AIST), and Jatco Ltd.). This system has been verified by the design engineers of Jatco Ltd. in actual product development. We report its effectiveness for predicting mechanical, electrical, and heat transfer failure, the verification of the system, and its validation in an actual design process. We conclude that the system can help design engineers to effectively and efficiently create FT diagrams in reliability engineering, although some existing ability in FTA and engineering is required. We also describe some outstanding issues regarding the improvement of FTAid, engineering education, and ensuring reliability.