Motion periods of sun gear dynamic fault meshing positions in planetary gear systems.

• The motion periods of sun gear fault meshing positions are studied in planetary gear systems. • Generalized expressions of the studied motion periods are derived and validated. • The influences of the motion periods to the vibration response are analyzed. • The minimal measured data length for effective fault diagnosis is recommended based on the motion period. Special assembly manner provides planetary gearboxes unique transmission characteristics, meanwhile brings the diagnostic complexity via a fixed sensor due to the irregular dynamic nature of gear fault meshing positions. This paper proposes a systematic scheme to explore the motion periods of the sun gear fault meshing positions in a planetary gearbox, namely tidal periods. The generalized expressions to the tidal periods are derived and validated through the operational mechanism of a planetary gearbox. The tidal periods are incorporated into simulated signal models so that the unique influences to the vibration responses of a planetary gearbox are revealed. Some previously uncleared and uninterpreted fault-related sidebands can, therefore, be properly interpreted. Moreover, a tidal period is proved to be a minimized time duration that embraces complete fault induced information. Through simple statistical analysis of experimental data under different operating speeds, a minimum required data length for proper fault diagnosis is recommended based on the analysis of a tidal period. The tidal period is an intrinsic nature due to the operational property of a planetary gearbox. [ABSTRACT FROM AUTHOR]