Research On Failure Propagation Mechanism Of CNC Lathe Based On Digraph

CNC Lathe is complex system that integrated with machine,electricity and liquid,the complexity of the system structure leads to the failure characteristics of propagation,hierarchy and concurrency.Machine operation failure is the coaction result of independent failure and cascading failure of components.If the propagation of cascading failure cannot be cut off in time,it will spread to the rest of the components because of the scale effect of system,resulting in the paralysis of machine.The propagation of cascading failure is closely related to the factors such as the structural features of failure propagation model among components,the component reliability level and the environmental impact.Failure propagation mechanism analysis is the fundamental guarantee for failure diagnosis and health maintenance,also one of the vital intelligent basic technologies of equipment.Therefore,the research on failure propagation mechanism of CNC Lathe has great significance to realize the intellectualization of manufacturing equipment.Support by Jilin Provincial Natural Science Foundation,taking a kind of domestic CNC lathe as research object,according to the failure mechanism analysis,define the failure propagation strength based on multi-indicators to characterize failure propagation behavior,combined with the hierarchy failure propagation digraph,then a key nodes and key path identifying method for failure propagation is proposed to research on the failure propagation behavior of CNC Lathe from microscopic to macroscopic,qualitative to quantitative.The main contents are as follows:(1)Construct failure propagation model of CNC Lathe system.Based on the failure mechanism analysis of CNC Lathe,the failure propagation digraph model is built by the digraph theory.With matrix tools,integrating DEMATEL/ISM method,realize the level structuring of model and obtain the initial hierarchy failure propagation digraph model to realize the system hierarchy and describe the failure step-diffusion process.Add virtual nodes to determine the hierarchy failure propagation digraph model of CNC Lathe system for the final key path identification.(2)Evaluate structural index of failure propagation model.First,with the initial hierarchy failure propagation digraph model,calculate the edge betweenness to measure the load capacity of each directed edge.Second,calculate the modified state transition probability matrix according to the direct influence matrix obtained by failure mechanism analysis.Introduce PageRank algorithm to evaluate the component node failure influence degree which provide the basis for the system failure source location.Combining with the initial hierarchy failure propagation digraph model,the edge failure influence degree is evaluated to realize the quantitative evaluation of failure influence between components.The edge failure influence degree and the edge betweenness both have effects on failure propagation behavior which will be considered as important parts for the identification principle of key path.(3)Identify key failure propagation path of CNC Lathe system.Based on CNC Lathe failure information,the failure probability of each component node in failure propagation model is evaluated reasonably.Propose a method of locating failure source based on the product of component node failure influence degree and the failure probability.Combine the component node failure probability with the structural indexes of failure propagation model to define the failure propagation strength as the identification principle of key path.Traverse all existent failure propagation paths in failure propagation digraph model to simulate failure step-diffusion process.Identify the key nodes of each level and the key failure propagation path.The proposed method reduces the deviation generated by existing method based on single index to simulate the failure propagation process and lays foundation for the realization of the system failure diagnosis.