MIMO testing on a car body using a three-dimensional scanning vibrometer

Experimental modal analysis on a car body requires multiple excitations and several hundred response degrees of freedom (DOFs). The applicability of a three-dimensional scanning vibrometer to the measurement task has been proven in this work. A three-dimensional scanning vibrometer measures the geometry and vibration data at all optically accessible points. The optical heads are moved to several positions around the car body, from each position the three-dimensional vibration data is acquired at some hundred points. For the described test, three shakers have been used simultaneously. Each shaker was driven with a non-coherent random signal. The transfer-functions from each shaker to each response point were calculated by principal component analysis. After the test, the results from the different laser positions were stitched, in order to display the operational deflection shapes of the entire car body. Then the data was exported via universal file for the purpose of performing a modal analysis.