A Novel Condition Monitoring Signal Analysis Method of Numerical Control Machine Tools in Varying Duty Operation

The internal sensor signals of the numerical controlled (NC) machine tools contain abundant information that associated with the operating state and the machining fault. However, the signal characteristics extracted in the time/frecquency domain miss its physical significance. This paper presents a signal preprocessing method in the spatial domain to extract the physical meaning characteristic of the internal sensor signals with the varying duty operation.The proposed method uses the encoder signal to resample the other condition signals in the spatial domain firstly. Then, the signals are analyzed by the Fourier transform to get the spectrum. Compared with the traditional methods, the physical meaning of the signal can be intuitively identified. Moreover, the characteristics can be obtained in the varying duty operation, instead of the uniform motion in the tradition methods. It is meaningful for the on-line monitoring, since the working condition of the machine tool is always changing in the machining process. The simulations and experiments verify the effectiveness of the proposed algorithm.