Abstract: To the early weak damage of the roller bearing and other rotating machinery, an enhanced resonance demodulation method based on delayed correlation pretreatment and entropy threshold of wavelet packet coefficients is proposed to solve the difficulty in determining the resonance bands in the traditional resonance demodulation technique. In this method, the weak damage signal should be preprocessed by using delayed correlation analysis method firstly. Then wavelet packet transform is carried out to find the Shannon entropy of all leaf nodes coefficients, an effective threshold is set on the basis of the entropy spectrum to choose the leaf nodes coefficients, reconstruct the signal, then do spectrum analysis, and extract the resonance modulation bands effectively. Then use the envelope demodulation method, and successfully extract the early impact characteristics of a weak damage signal of the machinery. The analysis results of roller bearing experimental data confirm the feasibility and validity of this method.

Key words: Bearing fault diagnosis, Entropy threshold, Resonance demodulation, Wavelet packet transform