Local fault diagnosis of non-stationary gearbox based on order envelope analysis

Gear tooth local fault is usually observed in gear system, it’s of significance to detect the gear tooth local fault during the operation process of the gearbox. However, the gearbox usually working in a non-stationary condition, namely the rotating speed or load are time varying, which increases the difficulty of fault diagnosis since the statistic features and spectrum vary by time. In this paper, an order envelope analysis method is proposed for fault diagnosis of a two-stage gearbox with local spalling fault and crack fault under non-stationary working conditions. Firstly, an accelerometer and an encoder are mounted on the gearbox to acquire non-stationary vibration data and rotating speed, respectively. After that, the angular resampling method is applied to convert the non-stationary time domain signal to angle domain signal by interpolation algorithm. Then envelope analysis is employed for the angle domain signals to detect the local fault characteristic frequency components in envelope spectrum. Finally, a new health inductor is proposed to detect spalling faults and crack faults in different working conditions. The fault diagnosis results show that the new method can effectively detect the gear local fault in various nonstationary working conditions.