Research on Modulation Mechanism of Planetary Gear Set Considering Time-Varying Transmission Paths with Manufacturing Error

Excitation is the main source of vibration in planetary gear systems. Due to coupling between different excitation sources and the modulation of vibration signals, rich sidebands exist in the measured vibration signals, making the fault diagnosis of planetary gear system rather challenging. By establishing an improved transmission path model, the effects of path length and material properties on signal attenuation are taken into consideration. Considering the internal excitation of time-varying meshing stiffness and geometrical error, the transfer path model and the internal excitation factors are integrated into the vibration signal model, and the signals collected by a vibration sensor are simulated and analyzed. Results show that the spectrum of the transfer path model can reflect richer sidebands around meshing frequency, which are related to the rotational frequency of the sun gear. In addition, the study shows that these components are caused by error excitations. Finally, the experimental signals are analyzed in detail to confirm the above simulation results. The simulation and experimental analysis demonstrate that the established model is helpful to understand the sideband characteristics of the vibration signals.