Experimental modal analysis using camera displacement measurements: a feasibility study

摘要

Recently, a mobile coordinate measurement machine consisting of three CCD cameras was expanded with dynamic measurement capabilities. The system is able to track three LEDs in three directions with a maximum sampling frequency of about 1000 Hz. This offers the possibility to use the measurements for dynamic system identification. To this aim, a vibrating structure is equipped with multiple lightweight infrared LEDs and excited by dynamic excitation sources. Transfer functions between force and displacements are estimated from which the modal parameters of the; structure can be identified. The benefits of using the camera displacement measurement system is that information down to 0 Hz can be obtained, that mounting LEDs is much easier than installing traditional displacement transducers (LVDTs) and that the coordinates of the measurement points are also available from the measurements. In this paper a dynamic testing study is performed using a scale model of an airplane. Both LEDs and accelerometers are mounted on' the structure allowing a comparison between displacement and acceleration transfer function modal analysis results. The main conclusion is that it is possible to successfully identify the modal parameters of the airplane scale model from the displacement measurements in the complete frequency range of the excitation.