A comparison of two modal analysis methods: An impact hammer versus laser vibrometry

Abstract

This paper presents a comparative experimental-analytical study on the performance of Multi-Input Single-Output (MISO) and Single-Input Multi-Output (SIMO) techniques to identify the modal properties of a cantilever beam. A 2-D laser interferometry was employed to perform the SIMO modal test, while for the MISO test configuration, a conventional accelerometer was used to measure the response of the structure. Comparing the experimentally-measured natural frequencies with those calculated by the FEM model, a maximum difference of 4% between natural frequencies was observed. The repeatability of both techniques is also investigated in this paper and it is shown that the difference between modal properties identified under different operators is less than 0.5% for both the MISO and SIMO techniques.This paper presents a comparative experimental-analytical study on the performance of Multi-Input Single-Output (MISO) and Single-Input Multi-Output (SIMO) techniques to identify the modal properties of a cantilever beam. A 2-D laser interferometry was employed to perform the SIMO modal test, while for the MISO test configuration, a conventional accelerometer was used to measure the response of the structure. Comparing the experimentally-measured natural frequencies with those calculated by the FEM model, a maximum difference of 4% between natural frequencies was observed. The repeatability of both techniques is also investigated in this paper and it is shown that the difference between modal properties identified under different operators is less than 0.5% for both the MISO and SIMO techniques.