Fault diagnosis techniques for planetary gearboxes under variable conditions: A review

Planetary gearboxes, as a key component of the transmission systems, are widely used in large-scale and complex mechanical equipment such as automobiles, helicopters, wind turbines and construction machinery. Due to working under the variable load and speed conditions, they are prone to failure and fault vibration signal generally exhibits many different characteristics from a planetary gearbox under stationary conditions. The existing fault diagnosis theories and technologies for gearboxes fail to effectively solve the difficulties in fault diagnosis of planetary gearboxes under variable conditions. The characteristics and difficulties of fault diagnosis for planetary gearboxes under variable operating conditions are analyzed, and the recent research developments are summarized from the aspect of vibration signal processing. Some key problems in current research are briefly discussed, and some suggestions are given for future research directions.