Abstract
In cases of reducing the number of modes in an operating response – for instance when using band pass filtering – often time domain identification techniques suffer from a tendency to over fitting. As a consequence, it might be useful to decrease the number of measured DOF’s to moderate the number of modes in the modal model. In these cases the dimension of the identified mode shapes is diminished accordingly and therefore it is preferable to have a way to expand back to the full set of DOF’s so that the estimated mode shapes can be animated in detail. In the present paper it is considered to use the correlation matrix for the filtered response including all measured DOF’s as a basis for the mode shape expansion. This matrix contains the normal modes that can easily be extracted from the column space of the correlation matrix. In this investigation the main focus has not been on the reduction problem, so engineering judgment has been used to secure a reasonable choice of reduced channels. The technique is illustrated on an OMA case where the modes of the tail part of a Panther helicopter is estimated during different flight conditions.
This is a preview of subscription content, log in via an institution to check access.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
References
Ibrahim SR, Milkulcik EC (1977) A method for direct identification of vibration parameters from the free response. Shock Vib Bull 47: 183–196
Ibrahim SR (1977) Random decrement technique for modal identification of structures. J Spacecraft Rock 14:696–700
Ibrahim SR (1978) Modal confidence factor in vibration testing. J Spacecraft Rock 15:313–316
Fukuzono K (1986) Investigation of multiple-reference Ibrahim time domain modal parameter estimation technique. M.Sc. thesis, Department of Mechanical and Industrial Engineering, University of Cincinnati
Vold H, Kundrat J, Rocklin GT, Russell R A multi-input modal estimation algorithm for mini-computers. SAE paper number 820194, 1082
Vold H, Rocklin GT (1982) The numerical implementation of a multi-input modal estimation method for mini-computers. In: Proceedings of the international modal analysis conference (IMAC), pp 542–548
Juang JN, Pappa RS (1985) An eigen system realization algorithm for modal parameter identification and modal reduction. J Guid 8(5): 620–627
Pappa RS, Elliott KB, Schenk A (1993) Consistent-mode indicator for the eigensystem realization algorithm. J Guid Control Dyn 16(5): 852–858
Pappa RS (1994) Eigensystem realization algorithm, user’s guide for VAX/VMS computers. NASA technical memorandum 109066
Camargo EA, Brincker R Operational modal analysis of a Panther helicopter during different flight conditions. To be submitted to XX
Brincker R, Ventura CE (2014) Introduction to operational modal analysis. Wiley
Acknowledgements
The financial support received from CAPES, through the Science without Borders Program, for this research, is gratefully acknowledged.
Author information
Authors and Affiliations
Corresponding author
Editor information
Editors and Affiliations
Rights and permissions
Copyright information
© 2015 The Society for Experimental Mechanics, Inc.
About this paper
Cite this paper
Brincker, R., Camargo, E.A., Skafte, A. (2015). An Example of Correlation Matrix Based Mode Shape Expansion in OMA. In: Caicedo, J., Pakzad, S. (eds) Dynamics of Civil Structures, Volume 2. Conference Proceedings of the Society for Experimental Mechanics Series. Springer, Cham. https://doi.org/10.1007/978-3-319-15248-6_38
Download citation
DOI: https://doi.org/10.1007/978-3-319-15248-6_38
Publisher Name: Springer, Cham
Print ISBN: 978-3-319-15247-9
Online ISBN: 978-3-319-15248-6
eBook Packages: EngineeringEngineering (R0)