Gearbox localized fault detection based on meshing frequency modulation analysis

Gearbox fault detection commonly relies on comparing sideband frequencies beside the meshing frequency of gear, and its harmonics of higher orders in frequency domain between the measured signal and healthy baseline. However, this type of localized fault detection algorithm is less intuitive and credible because other factors, such as manufacturing and assembly errors, can lead to similar sidebands without a localized fault. As such, this study proposes a novel and direct gearbox-localized fault detection strategy by taking full advantage of the meshing frequency modulation characteristic. During application, a baseline frequency band that is modulated by the meshing frequency was first located via a signal decomposition algorithm and meshing frequency modulation (MFM) index under healthy conditions. The raw signal was then analyzed using the same process. If there is a localized fault in the monitored gearbox, the bandwidth of the baseline frequency band will increase. Subsequently, a new frequency band will emerge around the higher-frequency zone, which is modulated by the gear meshing frequency. Compared with a healthy condition, a gear fault introduces a new MFM area. The usefulness of the proposed algorithm was demonstrated using the synthetic signal and experimental signal from the testrig.