Meshing frequency modulation (MFM) index-based kurtogram for planet bearing fault detection

Identifying the bearing fault-induced impulsive components in the frequency domain is a key step in the corresponding fault detection. However, gearbox vibration signals often significant interrupt the rolling bearing fault diagnosis, particularly in the detection of planet bearing faults under the background noise of the planetary gearbox. Except in the case of a high amplitude, a gear meshing-related vibration may also affect the identification of the planet bearing fault-induced resonance frequency band. To solve this problem, a meshing frequency modulation index (indexMFM)-based kurtogram utilizing a particular gearbox related phenomenon is proposed. The underlying mechanism is such that although the gear meshing-related spectral components are always more prominent in relatively higher-frequency band than the planet bearing-induced resonance frequency band in impulsiveness, the gear meshing-related impulsive components modulate the gear meshing frequency, yet the faulty bearing-induced one does not. Exploiting this difference, the planet bearing fault-induced impulsive components can be directly identified from the strong gear vibration interruption by determining the bearing fault-related resonance frequency band in the indexMFM-based kurtogram. The effectiveness of the proposed method is separately verified using simulated and experimental data.