Generalized Transmissibility Damage Indicator with Application to Wind Turbine Component Condition Monitoring

Frequency methods such as frequency spectrum
analysis, frequency spike detection, demodulation, envelope spectrum
method have been widely used for condition monitoring of
engineering structural systems. Different from the conventional
frequency methods, the transmissibility function (TF) represents
the relationship between different system output responses such
as, e.g. vibration and acoustic emission sensor measurements.
This paper introduces a simple and effective generalized transmissibility
damage indicator (GTDI) for TF based condition
monitoring. Unlike the conventional transmissibility damage indicator
(TDI), the new GTDI can improve the detection sensitivity,
reduces noise effects and avoid dynamic loadings effects. This is
achieved by combining multiple groups of data to obtain more
accurate transmissibility analysis, exploiting all the available
TFs, and using multiple references. This has two advantages.
First, it does not require any other priori knowledge about
the system responses. Therefore the method can be used for
the condition monitoring of a wide range of components or
systems. Further, the method can be easily implemented using
Fast Fourier transform (FFT) or power spectra density (PSD)
methods and therefore is computationally efficient. These make
the method very suitable for implementing online real-time
condition monitoring. The method is investigated by simulation
studies and then applied to analyze the vibration data of the main
bearing of operating wind turbines, producing very promising
results.