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Proceedings Paper

Normal mode testing using a scanning laser Doppler vibrometer
Author(s): A. Brehmer
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Paper Abstract

This paper presents a method to measure responses for a sinusoidally excited structure using a continuously scanning Laser Doppler Vibrometer (LDV). The LDV output signal is an amplitude-modulated vibration, whereby the excitation signal will be modulated by the response of the excited structure. Using an applicable demodulation the mode shape defined along a scan line can be derived by the envelope of the modulated vibration. By using an adaptable digital low-pass filter and parallel measuring of responses and mirror drive signal in the time domain the mode shape can be directly derived from the measured response. So the demodulation is a fast method to identify the mode shape from the measured response, because of its completion in the time domain. For that purpose the method is capable for using the responses online for normal mode tuning. Furthermore it is necessary for normal mode testing to measure complex responses to make an affirmation about the separation of real mode shapes. The method will match these requirements.

Paper Details

Date Published: 22 May 2000
PDF: 10 pages
Proc. SPIE 4072, Fourth International Conference on Vibration Measurements by Laser Techniques: Advances and Applications, (22 May 2000); doi: 10.1117/12.386713
Show Author Affiliations
A. Brehmer, DLR (Germany)


Published in SPIE Proceedings Vol. 4072:
Fourth International Conference on Vibration Measurements by Laser Techniques: Advances and Applications

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