Abstract: Planetary gearboxes are widely used in large-scale and complex mechanical equipments such as wind turbines, helicopters, construction machinery, etc. Low-speed and heavy-duty operation conditions frequently cause faults, such as severe pitting and fatigue crack etc., occurrence in the key components of the planetary gearboxes. The existing fault diagnosis theory and technology for traditional gearboxes (fixed-shaft gearboxes), however, fail to effectively solve the difficulty in the fault diagnosis of planetary gearboxes. In the planetary gearboxes, multiple mode mixing and complicated vibration transmission paths make fault response quite weak; large-range and instantaneous load fluctuation causes vibration obvious nonstationarity; the vibration responses of multiple meshing gear pairs couple with each other and correspondingly lead to evident nonlinearity; low-frequency characteristics are easily buried by heavy noise. The characteristics and difficulty of planetary gearbox fault diagnosis are discussed, and the inland and overseas research advances are reviewed from dynamic modeling and dynamic signal processing. The existing key problems in the current research are pointed out and the approaches to these problems are discussed.

Key words: Dynamic models, Fault diagnosis, Planetary gearboxes, Signal processing