Locating faulty planet gears using external vibration measurements


In this study, we develop a mesh phasing based approach to locate the position of faulty planet gears using external vibration measurements. Previous studies have illustrated how this can be done using internal vibration measurements recorded from a sensor placed on the planet carrier. It was shown in those studies that the timing of identifiable fault symptoms in the vibration signal relative to the phase of the gearmesh component depends on which planet gear carries a fault. A signal processing technique was then developed to locate the position of a spalled gear using internal vibration measurements. However, internally mounted sensors are not commonly used in planetary gearboxes, and it is much more convenient to mount sensors externally, on the gearbox casing for example. Therefore, this study extends the concept of using mesh phasing relationships to locate faulty planet gears, this time using external vibration measurements. The updated procedure is validated using experimental data collected from a test rig running under a range of operating conditions. The results show that the updated procedure is able to identify the location of faulty planet gears so long as an absolute phase reference (e.g., from a tachometer) of the planet carrier is available.