Use of mesh phasing to locate faulty planet gears

It is a challenge to determine by vibration analysis which planet gear carries a fault due to the complex layout of planetary gearboxes. In this study, we explain for the first time the possibility of using mesh phasing for distinguishing between faults on different planet gears. It has been found that, due to mesh phasing relationships, the vibration signals recorded on a planetary gearbox test rig exhibit different characteristics depending on the position of the faulty gear. These tests used localised seeded spalls giving impulsive signals, and it was found that due to the sequential mesh phasing arrangement, the timing of the fault-related impulse responses, as measured relative to the phase of the gearmesh component, depends on which planet is faulty. These timing differences can also give rise to different levels of asymmetry in the signal. This paper proposes a phase-based approach to differentiate and locate the faulty planet gear position using vibration response signals, and an indicator is developed for this purpose. With the assistance of absolute phase information, acquired through a tachometer on the planet carrier, the phase indicator is able to locate the position of the faulty gear. The approach has been applied to recorded experimental signals and it is found that the method can diagnose the position of the faulty gear effectively. (C) 2018 Elsevier Ltd. All rights reserved.