Output-only Modal Analysis by Frequency Domain Decomposition

In this paper a new frequency domain technique is introduced for the modal identification of output-only systems, i.e. for the case where the modal parameters must be estimated without knowing the input exciting the system. By its user friendliness the technique is closely related to the classical approach where the modal parameters are estimated by simple peak picking. However, by introducing a decomposition of the spectral density function matrix, the response spectra can be separated into a set of single degree of freedom systems, each corresponding to an individual mode. By using this decomposition technique close modes can be identified with high accuracy even in the case of strong noise contamination of the signals. Also, the technique clearly indicates harmonic components in the response signals.

[1]  Palle Andersen,et al.  Modal Extraction on a Diesel Engine in Operation , 2000 .

[2]  Palle Andersen,et al.  Modal Testing of Mechanical Structures Subject to Operational Excitation Forces , 2001 .

[3]  Jer-Nan Juang,et al.  An eigensystem realization algorithm for modal parameter identification and model reduction. [control systems design for large space structures] , 1985 .

[4]  B. Moor,et al.  Subspace identification for linear systems , 1996 .

[5]  Palle Andersen,et al.  Output Only Modal Testing of a Car Body Subject to Engine Excitation , 2000 .

[6]  Rune Brincker,et al.  IMAC : Proceedings of the 18th International Modal Analysis Conference (IMAC), San Antonio, Texas, USA, February 7-10, 2000 , 2000 .

[7]  Andreas Johann Felber,et al.  Development of a hybrid bridge evaluation system , 1994 .

[8]  S. R. Ibrahim,et al.  The Experimental Determination of Vibration Parameters from Time Responses , 1976 .

[9]  Carlos E. Ventura,et al.  Structural assessment by modal analysis in Western Canada , 1997 .

[10]  J. Bendat,et al.  Random Data: Analysis and Measurement Procedures , 1971 .

[11]  Julius S. Bendat,et al.  Engineering Applications of Correlation and Spectral Analysis , 1980 .

[12]  Richard Russell,et al.  A Multi-Input Modal Estimation Algorithm for Mini-Computers , 1982 .

[13]  Palle Andersen,et al.  Comparison of System Identification Methods using Ambient Bridge Test Data , 1999 .

[14]  Rune Brincker,et al.  Ambient Response Analysis of the Heritage Court Tower Building Structure , 2000 .