A complex filter for vibration signal demodulation in bearing defect diagnosis

In this paper, a complex filter for Hilbert transform is proposed to apply in the real-time vibration signal demodulation. The filter could provide a complex signal directly, as a function of both frequency and time, and the envelope could be derived from the absolute value of the complex signal. Three parameters, the scaling factor, center frequency and passband width, are designated to achieve the satisfactory properties of fast waveform convergence, constant passband gain and little phase distortion. Thus, a finite waveform interval of the proposed filter could be possibly applied in the vibration signal demodulation. From theoretical analysis and experimental studies, it is shown that the proposed filter could be effectively applied in the real-time vibration signal demodulation for a roller bearing system.