Zero Phase Wavelet Transform for Detecting Bearing Localized Defects

Abstract

This study designed a wavelet in such a way that its Fourier transform has zero phase (hence the name zero-phase wavelet). Since the wavelet has zero phase, the resulted wavelet transform’s phase part solely depends on the phase of the signal within the passing band of the wavelet used. With its ability to localize in time and frequency domains, the magnitude part reveals local amplitude modulation and the phase part reveals local phase modulations associated with the frequency band defined by the wavelet. This study established the utility of the zero phase wavelet for bearing localized defect detection, examined the magnitude and phase of zero phase wavelet transform of bearing signals to determine if they can detect periodic structural ringings as effectively as the prevailing envelope spectrum technique and if the phase part brings any additional diagnostic information. It was found that the zero-phase wavelet transform is more effective than the envelope spectrum and the additional phase information complements the amplitude information and enhances the sensitivity for the detection.