Abstract: Based on the local characteristic-scale decomposition (LCD) and the empirical envelope (EE) demodulation, a new non-stationary signal analysis method is put forward. By using the LCD a complex signal can be decomposed adaptively into some intrinsic scale components (ISC) and a trend. The EE technique is utilized to demodulate the ISCs and the instantaneous amplitudes and frequencies of them are obtained. The whole time-frequency distribution of the original signal is acquired. The newly proposed approach is compared with the Hilbert-Huang transforms (HHT) method as well by analyzing the simulation signals. The results indicate that the newly proposed method is superior to the HHT method in restraining the end effect, iteration time and the accuracy of the instantaneous characteristics. The time-frequency method based on the LCD and EE demodulation is applied to the mechanical fault diagnosis. By analyzing the experimental data, the results show that the time-frequency method based on the LCD and the EE demodulation approach can extract the fault characteristics of mechanical vibration signals and can fulfill the fault diagnosis efficiently.

Key words: Empirical envelope method, Fault diagnosis, Instantaneous frequency, Local characteristic-scale decomposition, Time-frequency analysis