Vibration analysis of a planetary gear with the flexible ring and planet bearing fault

Abstract Vibration performances of planetary gears are greatly affected by the flexible ring gear and planet bearing faults. However, the previous works only considered single flexible ring gear, rigid planetary gear system or planet bearing fault in their models. To overcome this problem, a flexible-rigid coupling dynamic (FMBD) model for a planetary gear is presented. Both the flexible ring gear, flexible supports of the ring gear and sun gear, and a rectangular local fault in the planet bearing are formulated in the presented FMBD model. The time-varying impulse force caused by the fault is described by a half-sine profile. Effects of the fault width, moment, and input speed on the time- and frequency-domain responses of the planetary gear are analyzed. To validate the presented FMBD model, the results from the FMBD model are compared with those from the experiment in the listed work. Note that the time- and frequency-domain responses from the flexible-rigid and rigid models are very different. Thus, the flexible ring gear should be formulated in the dynamic models of planetary gear, as well as the flexible supports of the ring gear and sun gear. The presented results can give some guidance for fault detection methods of planet bearings.