Research On Reliability Evaluation Of Motorized Spindle Based On Field Tracking And Laboratory Bench Test

The motorized spindle mainly plays the role of transmission speed and output torque in the machining process of CNC machine tool,which is the key to affect the reliability level of the whole CNC machine tool,and belongs to one of the key functional components.It is of great significance to study the reliability of motorized spindle for improving its reliability and ensuring the reliability level of CNC machine tool.The motorized spindle is a typical product with long life and high reliability.The traditional reliability test method is difficult to produce large sample fault data,which does not meet the technical requirements of large sample reliability evaluation method.Motorized spindles have obvious index degradation characteristics in the application process.How to realize high-precision reliability evaluation of motorized spindles with the help of degradation data has always been the focus of attention of scholars and engineers.The research on reliability evaluation method of motorized spindle based on degenerated data is still in the preliminary stage,and there are some problems such as single data source and difficult calculation,which affect the accuracy of reliability evaluation results of motorized spindle.Aiming at this problem,this paper takes machine tool motorized spindle as the research object,fuses the degradation data of laboratory reliability bench test and field data and other dual-source data,establishes the reliability model of motorized spindle performance degradation,and realizes the reliability evaluation of motorized spindle with dual-source data fusion.Main research contents of this paper:Firstly,the basic structure and working principle of the motorized spindle are analyzed,and then the failure mechanism of the motorized spindle is analyzed,and the degradation index and load simulation stress of the reliability test of the motorized spindle are determined.Considering the limitation of the reliability test time and test equipment of motorized spindle,the accelerated degradation test and field test of motorized spindle reliability bench were carried out,and the degradation data of motorized spindle were collected,and the degradation data were processed and the performance degradation curve of motorized spindle was drawn.Secondly,the common degradation models,standard Wiener processes and linear Wiener processes are summarized.According to the characteristics of motorized spindle,a method to describe the performance degradation process of motorized spindle based on nonlinear Wiener process was proposed.Based on the assumption that the increment of random variable obeys normal distribution,the failure time of the motorized spindle is predicted with the given fault threshold,and then the reliability model of the motorized spindle is given.Thirdly,on the basis of the motorized spindle degradation model established,the maximum likelihood estimation method is used to estimate the on-site reliability model parameters of the motorized spindle with a single data source and evaluate the reliability of the motorized spindle.The joint density function of the laboratory degradation model and the field degradation model was given by the appropriate Copula function.The unknown parameters of the edge distribution model were estimated by the two-stage estimation method,and then the reliability of the motorized spindle was evaluated.Finally,taking the parameters of the laboratory degradation model as the prior distribution,the posterior distribution of the unknown parameters in the degradation model was estimated by the Bayesian method and Gibbs algorithm,and the reliability of the motorized spindle was evaluated.In addition,the reliability of motorized spindle evaluated by single source data maximum likelihood estimation method,dual source data Copula function method and Bayesian method is compared and analyzed,which verifies the advantages of Bayesian method in simple calculation and relatively accurate results.By comparing the reliability of different degradation models of motorized spindle,it is proved that nonlinear Wiener process can describe the degradation trajectory of motorized spindle.