The Methodology of Modified Frequency Band Envelope Kurtosis for Bearing Fault Diagnosis

Recently, the enhanced frequency band entropy (EFBE) was proposed based on the replacement of short-time Fourier transform with wavelet packet transform. In view of the shortcomings of EFBE, a feasible solution is provided, namely modified frequency band envelope kurtosis (MFBEK), which can be described as follows: First, the modified adaptive resonance bandwidth (MARB) based on the bearing inner-race fault frequency is proposed. The kurtosis of the envelope signal as an available indicator and the MARB are used to determine the optimal depth of MFBEK. Second, this special case, that is, the resonant frequency occurs at the junction of two adjacent subbands is considered, and a corresponding effective solution is provided to determine the optimal subband(s). Then, the reconstructed signal can be obtained. And then, if necessary, a band-pass filter is designed to process the reconstructed signal to enhance the noise reduction performance. Finally, envelope power spectrum analysis is performed on the reconstructed signal or the filtered signal to extract the fault characteristic frequency. In addition, a modified indicator is proposed to measure the analysis results. Analysis results on simulated and vibration signals measured from actual bearing have revealed that the MFBEK can obtain more robust performance.