Measuring mode shapes with a continuously scanning laser vibrometer - Hilbert transform approach

Abstract

This paper is concerned with vibration deflection-shape measurement techniques for a sinusoidally excited structure, using a continuously scanning laser Doppler vibrometer (CSLV). The CSLV output signal is an amplitude-modulated vibration in which the excitation signal is modulated by the (complex) deflection shape, and thus the deflection shape, defined along a scan line, can be derived from the envelope and phase information in the CSLV output signal. In this work, a Hilbert transform based approach has been proposed for measurement of deflection shapes. This is a simple technique, which has advantages over previously described demodulation and Fourier transform approaches. The feasibility of the proposed technique is illustrated, along with results of an experimental demonstration. (C) 2002 Elsevier Science Ltd. All rights reserved.