Enhanced order spectrum analysis based on iterative adaptive crucial mode decomposition for planetary gearbox fault diagnosis under large speed variations

•A novel time-frequency analysis method, named iterative adaptive crucial mode decomposition (IACMD) is proposed, which not only can accurately extract the crucial dynamic components from non-stationary signals, but owning good parameter adaptability and low calculate consumption.•An enhanced order analysis scheme based on IACMD is put forward for planetary gearbox fault diagnosis, which is effective even if when suffering large speed variations and strong interferences.•The instantaneous phase of the rotating shaft is solved by the reciprocal of a specific order in the envelope order spectrum without referring to any speed information.