A Dual Beam Laser Vibrometer for Measurement of Dynamic Structural Rotations and Displacements

A novel non-contacting system for multiaxis vibration measurements (one translation and two angular deflections) is described. The system is based on monitoring the reflections of two laser beams from a planar reflective target. By utilizing the geometry of the beams and their respective reflections: range, pitch and roll of the target can be determined. The theory behind the system is discussed along with the development of a prototype device. Static and dynamic experiments are performed to determine the system's operational limits and utility. The prototype system demonstrated the capability of measuring motions up to 1 kHz with absolute accuracies of 0·04 mm for the translation variable and 0·03 degrees for the rotation variables. Measurement precision of 0·01 mm and 0·01 degrees approached the precision of the test stand and the theoretical resolution limits of the system over a usable workspace of ±2·5 mm and ±5 degrees.