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Harmonic and modal frequency discrimination in time domainoperational modal analysis

Published online by Cambridge University Press:  06 February 2014

V.H. Vu ,
M. Thomas  and
F. Lafleur
V.H. Vu
Affiliation:
École de Technologie Supérieure, 1100 Notre Dame West, Montréal, Qc, H3C 1K3, Canada
M. Thomas*
Affiliation:
École de Technologie Supérieure, 1100 Notre Dame West, Montréal, Qc, H3C 1K3, Canada
F. Lafleur
Affiliation:
Institut de recherche d’Hydro Québec, 1800 Bl. Lionel-Boulet, Varennes, J3X 1S1, Canada
*
a Corresponding author: [email protected]
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Abstract

An algorithm of operational modal analysis in time domain is presented for thediscrimination between structural modes, harmonic excitations and spurious modes. Aclassification factor is developed and based on the construction of the damped signal- to-noise ratio which separates the physical modes from the numerical ones. The harmonicexcitations are then recognized at very high power indexes and zero damping. Furthermore, after the modal discrimination, the harmonic spectrum and the estimated frequency responsefunction can be derived. The method can be updated in the time domain either by a shorttime sliding window or a recursive technique to provide the modal monitoring in bothstationary and non-stationary process. An industrial application on a hydro-electricalgenerator is discussed to identify the machine frequencies under operational workingconditions.

Keywords

Modal identificationmode separationrecursive analysisshort-time modelingnon-stationary vibrationhydro-electric generator
Type
Research Article
Information
Mechanics & Industry , Volume 15 , Issue 1 , 2014 , pp. 29 - 37
Copyright
© AFM, EDP Sciences 2014

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References

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