Recovery of Mode Shapes from Continuous Scanning Laser Doppler Vibration Data: A Mode Matching Frequency Domain Approach

Abstract

The paper illustrates a method for processing, in a blind way, data obtained by Continuous Scanning Laser Doppler Vibrometry (CSLDV). CSLDV makes it possible to measure the structure vibration joining together the spatial and time information. The vibration datum obtained from the laser, which continuously scans (over time and space) the structure under test, is in fact modulated by the Operational Deflection Shape (ODS) excited during the experiment. The idea that we propose in this paper is based on the fact that, if the mode shapes of the structure under test are known a priori, e.g. from a numerical model or from an analytical formulation, it is possible to settle a procedure that searches for similarities between those known mode shapes (the candidate mode shapes) and ODSs that actually modulate the signal. This procedure can be considered a pattern matching technique that makes it possible to identify the resonance frequency related to each ODS and the mode shapes that better match with ODSs excited. A detailed description of the algorithm is given in this paper.KeywordsLaser doppler vibrometryContinuous scanning laser doppler vibrometryPattern matchingVibration testingMode matching