Condition monitoring of variable-speed and -load machinery using time-frequency distributions

Spectral analysis using the standard Fourier Transform approach is the most commonly used processing technique for evaluating the mechanical condition of machinery working in stationary regimen. However, in machinery operatin g in transient modes, such as variable-load and/or -speed which generate si gnature spectra that at each instant of time have a distinct frequency cont ent, this standard approach is not directly applicable for analysis. New tr ansforms, called time-frequency distributions (TFD), offer unique tools for non-stationary signal analysis. In this work the most appropriate TFDs for the analysis of transient vibratory signals in machines are analysed. A pr actical example showing the application of the TFD to a time signal measure d on hoist transmission of a shovel is also presented.