Localized faults detection of planetary gear sets based on resonance demodulation and vibration separation

Due to the epicyclic motion of planet gears, the vibration picked up from planetary gearboxes is significantly different from that from the fixed-axis gearboxes. In particular, the vibration transmission path is time-varying. Hence, it is difficult to detect localized gear faults of planetary gearboxes. In order to address this issue, a constructive method is proposed in this paper, which combines vibration separation, order tracking, and resonance demodulation analysis approaches. Firstly, the complex envelope of the vibration is extracted by the fast kurtogram algorithm. Then, the envelope is equi-angle resampled to eliminate the inevitable speed fluctuations. Subsequently, an appropriate window function is used to grab vibration at a fixed angular position of the carrier according to the tooth meshing characteristics of the gear sets. Then, the synchronous averaging is applied to an artificial gear vibration, which is constructed by connecting the grabbed data blocks according to the teeth sequence of the interesting gear. Finally, the envelope order spectrum is utilized to expose the faults characteristics. The effectiveness of the proposed method is validated by comparative experiments with the normal and faulty gear sets.