CAD for fault tree-based diagnosis of industrial processes

Abstract Despite extensive research in the area of model-based fault diagnosis, the number of applied solutions is still rather limited. The reason for this is to be partly sought in the relatively high costs related to the development of a diagnostic system. Hopefully, the efficiency of the development cycle can be substantially improved with the use of computer-aided design (CAD) tools. This fact served as a major motivation for the realisation of a CAD prototype which performs automatic synthesis of rule-based diagnostic systems for industrial processes. The tool relies on fault propagation models and an object-oriented modelling paradigm. A model of the whole process derives from the component models and information about the way the components are interconnected. As the library of component models is inherent to the tool, the major input expected from the user is a process flowsheet. This can be simply provided through a graphic user-interface. The synthesis of propagation models, and synthesis of the rules thereof, is performed using an automatic synthesis procedure. An algorithm that transforms fault trees into event trees and diagnostic rules is presented. Handling complex structures, such as feedback loops, is also addressed. For on-line execution of the resulting diagnostic rules, the approximate reasoning scheme referred to as the transferable belief model (TBM) is suggested. The underlying CAD tool is suitable for performing several routine tasks that occur in the process of the development of a diagnostic system. This is illustrated on an example of a laboratory test rig.