Compensation for vibration signal power variance when changing equipment speed mode

Abstract

The purpose of this paper is to develop a method to enhance reliability of vibrational diagnosing of variable-speed industrial equipment. A dataset of vibration acceleration signals, picked up at the variablespeed test stand, has been obtained. Preliminary splitting of a vibration signal into three frequency ranges has been proved to be necessary. Vibration power dependencies on the main shaft speed have been estimated in different frequency ranges. The paper proposes an algorithm compensating variations of instantaneous power of vibration signal where equipment operation speed varies. It is based on the use of empirical dependencies of vibration signal power on shaft speed, which were derived by ensemble averaging of preliminarily split signals. A root mean square (RMS) value calculated in a sliding window is used to estimate variation of signal power. For signals within each frequency range, ensemble-averaged relative power variation produced by speed deviation is to be estimated. Instantaneous values of signals in each frequency range are to be divided by relations estimated as above. Thus, only power variations caused by variable speed are compensated. Variations caused by defect evolution are preserved. The resulting signal to be further analysed is derived by summation of processed signals in three frequency ranges. Power variation compensation decreases dispersion of parameters of signal that are used for estimation of equipment state. Preliminary compensation of vibration power variation caused by variable operation speed has proved to be effective for improving vibrational diagnostic system results. The proposed algorithm was validated on such statistical parameters of vibration as RMS and peak-factor of vibration signal.

Keywords

• vibration-based diagnostics
• digital signal processing
• equipment diagnostics