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Shock and Vibration
Volume 2015, Article ID 537030, 5 pages
Research Article

Modal Appropriation for Use with In-Operation Modal Analysis

1ISSAT Sousse, Avenue Ibn Khaldoun, Taffala, 4003 Sousse, Tunisia
2University of Michigan, Ann Arbor, MI 48109, USA

Received 30 May 2014; Revised 21 November 2014; Accepted 25 November 2014

Academic Editor: Chao Tao

Copyright © 2015 M. Abdelghani and D. J. Inman. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We propose in this paper a numerical modal appropriation method for use with in-operation modal analysis (INOPMA). The key idea is to realize that the correlation sequence of the system output is the sum of decaying sinusoids with a certain phase shift and therefore it may be considered as an impulse response. The method is based on performing a numerical convolution of a single sine wave force with the system output correlation sequence. The steps are then similar to the classical modal appropriation method, although the characteristic frequencies are different. This approach is validated and compared to a subspace method on simulated data as well as on experimental data and it is shown that INOPMA outperforms the subspace method.