Machinery diagnostic application of the Morlet wavelet distribution
Howard A. Gaberson · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2001
The Morlet wavelet distribution is a time frequency distribution that can be described as a convolution of the wavelet with a vibration signal for various scales or frequencies. The Morlet wavelet, which is a Gaussian windowed complex sine wave, analysis has several subtle programming implications that both relate to and differentiate it from the short time Fourier transform. These are described, discussed, and tested on machinery vibration signals with positive results. Traditional scale with its octave representation is discarded in favor of equally spaced frequencies. A window width factor is tested to emphasize precision in either time or frequency. A variable length exponential window is necessary as a function of frequency and the width factor. The analysis is coded in MATLAB efficiently using their `conv' algorithm, and results of applying it to machinery diagnostic vibration signals are presented.