Two new features for condition monitoring and fault diagnosis of planetary gearboxes

Planetary gearboxes are widely used in aerospace, automotive and heavy industrial applications that require compactness and high torque-to-weight ratios. Despite these advantages, tough operation conditions under which planetary gearboxes are typically used may lead to damage on their key components, for example, gears and bearings. Because of the unique behaviors of planetary gearboxes significantly different from fixed-axis gearboxes, the diagnostic features developed and working well for fixed-axis gearboxes will degrade when applied to planetary gearboxes. Therefore, there is a demand to develop features specifically for monitoring and diagnosing planetary gearboxes. To meet this demand, this paper proposes two features, namely, accumulative amplitudes of carrier orders and energy ratio based on difference spectra. The effectiveness of the proposed features is demonstrated using the vibration data acquired from a planetary gearbox test rig. The vibration data is measured under different motor speeds and various types of faults on gears and bearings. The proposed features are also compared with those reported in the literature. The comparison results show that the proposed features are more successful than others in monitoring and diagnosing planetary gearboxes.