  The novelty of the current work is precisely to propose a statistical
procedure to combine estimates of the modal parameters provided by any set of
Operational Modal Analysis (OMA) algorithms so as to avoid preference for a
particular one and also to derive an approximate joint probability distribution
of the modal parameters, from which engineering statistics of interest such as
mean value and variance are readily provided. The effectiveness of the proposed
strategy is assessed considering measured data from an actual centrifugal
compressor. The statistics obtained for both forward and backward modal
parameters are finally compared against modal parameters identified during
standard stability verification testing (SVT) of centrifugal compressors prior
to shipment, using classical Experimental Modal Analysis (EMA) algorithms. The
current work demonstrates that combination of OMA algorithms can provide quite
accurate estimates for both the modal parameters and the associated
uncertainties with low computational costs.
