Research On CBR And Multi-Agent Based Distributed Fault Diagnosis System

Modern fault diagnosis system is a dynamic, distributed, flexible and uncertain complicated system. Multi-Agents can make use of distributed process technology and modular design thoughts, and devide the complicated system into several relatively independent subsystems, then solve the complicated diagnosis problem through the cooperation and competition of Multi-Agents, considering that aboundant fault diagnosis cases had been accumulated in daily maintenance work, the thesis researches how to combine the CBR and Multi-Agents technologies in the distributed fault diagnosis systems accordingly.Firstly, the paper introduced the survey of modern fault diagnosis systems and summaried the mechanisms of artificial intelligence in fault diagnosis systems, then, introduced Case-based reasoning(CBR), Agent technology and the Multi-Agent system in brief, a distributed fault diagnosis system structure model was constructed based on the CBR and Multi-Agent technologies. Secondly, Each function agent in the structure model was analyzed in detail; meanwhile, the paper researches the cooperation mechanisms which based on the scheme of voting of many CBR-Agents, and three kinds of distributed trust management methods are introduced in the structure model, those were numeric idiograph, access control table and roles based access control, and the paper disscussed the safety model of case retrieving agents in the structure model.Thirdly, the thesis applied the structure model of distributed fault diagnosis to the civil aircraft fault diagnosis systems. The paper researched the key technologies of CBR method in the civil aircraft fault diagnosis: Applying the gray theory to the case similarity computation, and the difference derived method to case adaption. Finally, a fault diagnosis system of civil aircraft was developed on the JADE platform, and realized the distributed cooperation diagnosis of many CBR-Agents based on contract network,as the combination of the CBR method and the agent technology,the system has the properties of collective intelligence,good robustness and better fault tolerance.