Application of wavelet packet to fault detection in rotating machinery and simulation of matlab

Orthogonal wavelet applied in wavelet transforms is only interested in orthogonal whereas makes a reduction in locality, so its sensibility to the local fault is lower, and calculation amount of continuous wavelet transform is lager than others. Therefore, an analysis method by means of wavelet packet transform to gear vibration signal is presented. The signal decomposition and reconstruction algorithm based on orthogonal multi-resolution analysis-Mallet and its improved algorithm are presented. We derive Mallat algorithm of wavelet packet transforms followed binary form. Then three-shaft gear box 6J90T, which is open-teeth, is adopted in the experiment. Preliminary decision is that fault happens on the gear of intermediate shaft. From the result through wavelet package of the gearbox that is showed as figure 1, We can see that the impulse interval is 80ms and the position signal conforms to the time domain signal. But these impulses visibly concentrate on the 300Hz frequency band in frequency domain. So the accident happened on the gear that make intermediate shaft and output gear engage. The fault detection experiment to the gearbox proved to be effective.