Development of a three-degree-of-freedom laser vibrometer system for the measurement of structural translations and rotations with applications

A noncontacting laser vibrometer triangulation system that simultaneously measures one dynamic translation and two dynamic rotations of a reflective surface was developed. The geometry of the design was numerically optimized yielding a measurement workspace of ;Some of the applications investigated with this device include modal analyses of a cantilever beam and a printed circuit board, and structural dynamics modifications using beam elements. The structural dynamics modification test was to convert an experimental modal database from a cantilever beam into a fixed/fixed beam. Comparison of the results from this procedure with experimentally measured values from a fixed/fixed beam showed excellent correlation. This was the first successful use of experimental rotational degrees of freedom in the structural dynamics modification process.