Cyclic-frequency-constrained time-frequency masking for fault feature extraction and diagnosis in rotating machinery

Accurate fault feature extraction is essential for analyzing rotating machinery measurement signals, especially when fault signatures are masked by strong noise and multi-source interference. In practical measurement scenarios, different bearing faults may excite adjacent resonance bands, while isolated impulsive disturbances may occur in the same carrier-frequency band as the target fault. These effects make it difficult for time-frequency methods to distinguish fault-related impulses from non-target components. To improve the selectivity of periodic transient extraction, this paper proposes a cyclic-frequency-constrained time-frequency masking (CFC-TFM) method. The cyclic modulation spectrum is first used to identify the target fault cyclic frequency and its associated carrier-frequency band. A cyclic modulation frequency mask (CMFM) is then constructed to constrain the resonance band, and a cycleconsistent time gate (CCTG) is developed to retain impulse instants consistent with the target fault periodicity. The CMFM and CCTG are then combined to form the final CFC-TFM. This combined mask selectively enhances faultrelated impulsive features while suppressing same-band isolated interference and adjacent fault components.Simulation and experimental results demonstrate that CFC-TFM produces clearer periodic impulse sequences and more distinct fault characteristic frequencies, providing an effective tool for fault-related feature extraction from complex rotating machinery measurement signals.