Use of Holo-Hilbert spectral analysis to reveal the amplitude modulation features of faulty rolling bearing signals

Time-frequency analysis (TFA) is a powerful tool for vibration signal analysis. However, it cannot comprehensively reflect the cross-scale coupling relationship between amplitude-modulated (AM) and frequency-modulated (FM) characteristics of the vibration signal collected from faulty rolling bearings. To address this shortcoming, the Holo-Hilbert spectral analysis (HHSA) method with combining the masking empirical mode decomposition (Masking-EMD) for signal separation is introduced to completely describe the internal modulation characteristics of faulty rolling bearing. In HHSA, first, the initial vibration signal of faulty rolling bearing is decomposed into numbers of intrinsic mode functions (IMFs) to extract its time-varying FM and AM characteristics. Next, the instantaneous frequency and the instantaneous amplitude of each IMF are estimated, respectively. Then, each first-layer IMF is decomposed into a series of IMFs with AM characteristics via reusing Masking-EMD. Finally, the FM and AM components are combined with their instantaneous modulation energy to realize the three-dimensional Holo-Hilbert spectrum (HHS). The simulation and experiment results illustrate that the introduced method can completely reveal the AM characteristics of non-linear vibration signals and the corresponding carrier frequency range.