Correlation Analysis And Reliability Allocation Of CNC Machine Tool Subsystems

CNC machine tools,an important indicator to measure the degree of industrialization of a country,are the focus of development of "Made in China 2025"and "Industry 4.0".Reliability,as an important index of CNC machine tools,has been paid more and more attention and development.Reasonable reliability modeling and reliability allocation method are the main contents and development direction of CNC machine tool reliability field.It is also an important process and method to improve the overall reliability of CNC machine tools.Through modeling the fault data of a CNC machine tool,considering the overall correlation optimization,the reliability allocation method is improved,and the reliability of the distribution results is predicted to improve the reliability of the whole machine.In this paper,the fault data of the machine tools are collected and analyzed,and the reliability modeling of the whole machine and its subsystems is carried out according to the effective fault data.The distribution of the fault data is fitted by probability diagram and maximum likelihood estimation method,and the hypothesis distribution is tested by the card method.Monte Carlo random sampling and Copula function are introduced to analyze the correlation among subsystems based on the reliability distribution function of the whole machine and subsystems.The correlation coefficients between subsystems are obtained by maximum likelihood estimation,and the subsystems are grouped according to the correlation coefficients to simplify the calculation and modeling problems in the correlation analysis.Based on the reliability function of each subsystem and the correlation coefficient among subsystems,the correlation model between subsystems is established.Considering the influence factors of CNC machine tools,the reliability allocation matrix is established,and the weight of each influencing factor is determined by entropy weight method to calculate the reliability allocation factor of CNC machine tools.The reliability allocation method is optimized and the reliability allocation parameter is assumed to make the improved reliability allocation method applicable to series but related systems.The reliability of CNC machine tools is predicted according to the reliability distribution results.The subsystems are simulated by Monte Carlo method according to the distribution of fault interval and distribution parameters.According to the distribution of the fault interval and distribution parameters,the subsystems were simulated by Monte Carlo,and the reliability model of the whole machine was established in the light of the simulation results.Comparing the reliability curve of the original machine,the reliability of the whole machine is improved,and the reliability allocation method considering the correlation is verified.