Multi-fault Diagnosis For CNC Machine Tools Based On Graph Theory

With the rapid development of modern manufacturing industry, the CNC machinetools have been widely used, and regarded as the core parts of the production andprocessing system. However, the functions and structures of the CNC machine tools arevery complex, which makes hard for the faults diagnosis. At the same time, a fault of anyparts or components can be easily triggered by other fault/faults. So the failure mightoccur mainly due to the multi-fault. Besides, features of the multi-fault have a series ofcharacteristics, such as hierarchy, complexity, delay, relevance and regularity, which makethe multi-fault diagnosis for CNC machine tools more complex and harder than the singlefault diagnosis. So, how to diagnose the faults and to fix quickly and accurately, after thefaults of the CNC machine tools occurred, have been the great problems which need to besolved.Multi-fault diagnosis bases the graph theory is an important direction in the field offault diagnosis for the CNC machine tools. This paper bases the graph theory, combineswith the grey relation theory, to study the multi-fault diagnosis for the CNC machine tools.The main research contents and results are as follows.(1) Illustrate the research content of the fault diagnosis; analysis the classification, thecontent and the development trend of the various diagnosis methods, especially for thegraph theory.(2) Explore the mechanism, the method and the process of the multi-fault diagnosisbases the graph theory for the CNC machine tools. Propose a series solution for theproblems such as the propagation model to express the relationship between each fault, thehierarchy algorithm to process the propagation model, the fault location algorithm forlocating the cause faults.(3) Introduce the fault location algorithm bases the grey relation theory to avoid theshortages of the fault location method bases the traditional FMEA. Redesign the severityrating criteria and the detectability rating criteria bases the characteristics of the CNCmachine tools.(4) Demonstrate the proposed approach in the case study, the results show that theproposed approach is more accurate than the traditional method, and proves to be more useful in the multi-fault diagnosis of the CNC machine tools.Finally, introduce the development of the original fault diagnosis system of the CNCmachine tools. This system can not only realize the diagnosis for the multi-fault, but alsocan manage the machine structure, fault information and knowledge database.