Rapid and Dense 3D Vibration Measurement by Three Continuously Scanning Laser Doppler Vibrometers

Abstract

This paper presents an investigation of rapid and dense three-dimensional (3D) vibration measurement by three continuously scanning laser Doppler vibrometers (CSLDVs) in a synchronously scanning mode, which means that three laser spots from three CSLDVs continuously move along the same scan trajectory and synchronously measure vibration of the same point on a surface. Three CSLDVs, i.e., Top, Left, and Right CSLDVs, are from a Polytec PSV-500-3D system and input signals to scan mirrors of each CSLDV are controlled by a dSPACE MicroLabBox control unit. The whole system is called a 3D-CSLDV system. Rotation angles of scan mirrors of Left and Right CSLDVs can be obtained from those of the Top CSLDV based on positional relations among three CSLDVs. With the proposed methodology, three laser spots from three CSLDVs can continuously move in a synchronously scanning mode. An experiment is conducted to obtain 3D operational deflecting shapes (ODSs) of a composite plate in a measurement coordinate system (MCS) by a 3D-CSLDV system. Results of 3D ODSs in the MCS are in good agreement with those from a PSV-500-3D system in a step scanning mode.