An identification algorithm for directing the measurement point of scanning laser vibrometers

Investigation of three-dimensional vibration measurement by a single scanning laser Doppler vibrometer

“…In Ref. [17], coordinates of four target points in the MCS and the VCS were used to calculate T and R, which are expressed as…”

“…Equation 8cannot either directly solve a case when target points are coplanar, since the second matrix on the right-hand side of Eq. (8) is almost singular [17] and the condition number of the matrix is large. With the VCS defined in this work, singularity of the matrix is caused by almost linear dependence of the first row of the matrix with its last row.…”

“…However, in this method, two direction cosine matrices with opposite sign angles are obtained and one needs to identify the correct one, which may not be easy. Xu and Miles [17] summarized an inverse method to obtain the matrix. However, the matrix obtained by this method is not guaranteed to be orthogonal.…”

“…Compared with the inverse method in Ref. [17], the proposed method can yield an orthogonal direction cosine matrix and be applicable to a 2D structure. Effects of the number of target points on the accuracy and stability of the proposed method are investigated.…”

Deploying successfully Laser Doppler Vibrometry techniques within the automotive NVH process

“…Even on structures where it is relatively easy to access and mount contacting sensors, the Laser Doppler Vibrometer (LDV), and particularity the Scanning Laser Doppler Vibrometer (SLDV) offer reduction in test setup time and sometimes even data acquisition time on test involving many physical points or Degrees of Freedom (DOF). The SLDV is the same as the LDV with the addition of two mirrors which allow the laser spot location to be moved horizontally and vertically on a test object [2,3]. Using mirrors to move the laser is faster and usually more repeatable then manually or mechanically repositioning a LDV on a tripod or other mount.…”