Vibration signal simulation and fault diagnosis of planetary gearboxes based on transmission mechanism analysis

Planetary gear transmission structures, consisting of sun gear, planet gears, ring gear, carrier etc., are more complex than fixed-axis gear transmission structures. In planetary gearboxes, the vibration responses of multiple gear pair meshing couple with each other, and the vibration transmission paths from gear meshing points to the fixed transducers are time-varying. Therefore, fault diagnosis of the planetary gearboxes is more difficult compared to that of fixed-axis gearboxes, in which the vibration simulation models are very important. By analyzing the transmission paths of each meshing vibration and synthetizing the phase differences between different meshing vibrations, vibration simulation models of the planetary gearboxes are constructed and the vibration signals based on the models are obtained. By comparing the signal characteristics of the faulty condition with the healthy one, faults of the planetary gearboxes can be diagnosed. The constructed models are characterized by considering multiple gear pair meshing and their phase relations, time-varying vibration transmission paths, modulations due to gear faults, etc. To test the proposed models, the vibration signals are measured from a planetary gearbox test rig under the healthy condition, the sun gear with a cracked tooth and a planet gear with a cracked tooth, respectively. The fault characteristics of the planetary gearboxes are summarized based on the comparisons of the vibration signals between the models and the experiments.