Tacholess computed order tracking method via STFT and Vold-Kalman filtering

Order tracking (OT) is considered as a classic and effective technique for the non-stationary vibration analysis of rotating machinery. Traditionally, additional hardware such as a tachometer is required to provide a reference signal. To extend the applications of the OT technique, some tacholess OT methods were proposed recently. However, they are only applicable to those with small speed fluctuations. A new tacholess OT method is established in this article, which is applicable to the cases with large speed variation such as in the run up/down processes. In this method, the instantaneous frequency of one harmonic of rotation frequency is first estimated by time-frequency analysis. Vold-kalman filtering is then employed to extract the harmonic from the overall signal. Finally, the original signal is resampled by using the instantaneous phase of the extracted harmonic. In this way, the OT method can be carried out without tachometer. Simulations and experiments show that the results obtained through this method are almost the same good as those obtained through a tachometer under large speed variation. Furthermore, an incipient fault of gear is detected efficiently for a gearbox by using this method under large speed variation.