An analysis method for the vibration signal with amplitude modulation in a bearing system

In this paper, an envelope detection method for the vibration signal with amplitude modulation is proposed. The method is to filter the vibration signal through a designated band-pass filter. According to the resonance of the vibration signal in the passband, the filtered signal would be decomposed into a sinusoidal function basis at the resonant frequency. Under the assumption of a stepwise function for the envelope signal, the envelope signal could be derived by the linear least-squares analysis. In addition, the filtered signal could be easily reconstructed from the envelope signal. Furthermore, the logarithmic transformation is applied in this envelope signal, the defect frequencies due to bearing defects could be more enhanced by suppressing the corresponding sidebands. However, the logarithmic transformation would have little effect in the spectrum for a normal bearing. Accordingly, logarithmic transformation would be helpful to apply the signal processing method in enhancing the defect frequencies for the bearing defect diagnosis.