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| Signed directed graph (SDG) is an important qualitative model that is used to describe large-scale complex systems and the cause-effect relationships among variables. It has been successfully applied in fault diagnosis, hazard assessment and other areas. In the fault isolation problem, the task is to find the fault origin that causes the abnormal phenomenon. However, as the basis of analysis, the inference method based on SDG, is simply a traversal search or a rule-based expert system. Because of the redundant or disordered information, the efficiency of these algorithms is quite low. Rough set theory provides an idea of handling vague information and can be used to data reduction, thus it can be introduced to the fault isolation problem (a kind of decision problems) to optimize the decision rules. The decision algorithm is proposed in this paper, in which the generation and reduction methods of the rules are related to the structure of the SDG model. We combine the algebraic and logical expression ways to achieve the purpose. Moreover, due to the convenience of expressing granularity, the decision algorithm is still applicable when the types of the faults we concerned are changed or reformed. Finally, an example of a 65t/h boiler system is carried out to illustrate and validate the proposed method, and some future trends of this method are also discussed. |
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| Keywords:Signed Directed Graph, Rough Set; Large-Scale Complex System |
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