Application of averaged instantaneous power spectrum for diagnostics of machinery operating under non-stationary operational conditions

Vibration analysis of machines operating under non-stationary operational conditions requires special attention. This refers to the necessity of use of order tracking algorithms together with additional advanced signal processing methods, especially when faults indicators of interest are located in resonance frequency ranges.Nowadays, cyclostationarity analysis becomes more popular in the field of mechanical systems signal processing. It has proven its functionality in diagnostics of rotating machinery in numerous cases. The paper introduces the method called averaged instantaneous power spectrum as a time–frequency representation of selected cyclic components. The purpose of proposed tool is to provide supplementary information about the character of the cyclic component of interest and to enhance conclusions drawn from classical vibrodiagnostics approach. The method is tested on a selected case of wind turbine drive train fault as typical example of machinery operating under non-stationary operational conditions. The averaged instantaneous power spectrum is applied to vibration signal components originated from rolling element bearings. In the paper, the capabilities and limitations of the proposed method calculated in angular domain are presented with the main focus on variable operational conditions.

► Overcoming common obstacles related to variable operational conditions of machinery.
► Examination of operational conditions of wind turbines.
► Benefits of advanced time–frequency analysis.
► New method for synchronous averaging in time–frequency domain of non-stationary signals.