Fault Diagnosis Approach Based on Qualitative Model of Signed Directed Graph and Reasoning Rules

Abstract

Signed Directed Graph (SDG) is a fault diagnosis method based on qualitative model and cause and effect analysis, first, it establishes the SDG of the systems and components, simplifies these SDGs corresponding to the fault patterns diagnosed, SDGs are described the many rules forms for shortening the calculating time, then expands the diagnosing rule with expert knowledge to construct the diagnosing rule bank of the system. Second, transforming the quantitative values of the system’s variables into qualitative values, the fault patterns can be primary diagnosed. And then the patterns that can not be distinguished are diagnosed by using Fuzzy knowledge to form a qualitative and quantitative model. The case studies show the improved method is valid.