Operational Modal Analysis with a 3D Laser Vibrometer Without External Reference

The use of Scanning Laser Doppler Vibrometers (SLDV) is a common practice in the context with modal analysis. 3D SLDV have been used with classical experimental modal analysis for several years. In this case, three laser heads, which simultaneously point to the same location, are used and an additional input reference signal is required to combine the results of consecutive records. In operational modal analysis the input reference signal is replaced by an output reference signal, which may be obtained, for example, from an additional vibrometer or accelerometer.