Instantaneous availability modelling of CNC machine tool based on functional data analysis

A new way to calculate the instantaneous availability of the computer numerical control(CNC) machine tool was proposed based on the functional data analysis method. Using the quartic Bernstein polynomial as basis function to smooth the reliability estimation values, as well as the least square method to estimate the fitting parameters of the basis function. The estimated maintainability was across-section adjusted according to the trouble occurrence time section. Based on the adjusted trend of maintainability, the Fourier basis function was chosen to smooth it. The fitting coefficients were solved by the non-linear least variance method. A model was built for the instantaneous availability of the CNC machine tool based on the functional linear regression model, and taking 18 machine centers as examples to verify the proposed model. The results showed that the proposed model gave out the correlation coefficient of 0.9641, being effective to evaluate the instantaneous availability of the CNC machine tool.