Measurement of structure dynamics using a tracking-interferometer

Abstract

Measurement of structural dynamics can be used for dynamic characterization, diagnostics, condition monitoring, analyzing sources of vibration problems, design optimization and, finally, as comparison data to improve computation results. Mainly for open surfaces in automotive and aerospace industries the modal testing is often performed using laser vibrometers. In the case of partially closed structures as machine tools, modal analyses comprises the three dimensional vibration measurements at up to several hundred points of the structure and is classically conducted using accelerometers. This paper presents a novel approach to perform modal analyses using a tracking-interferometer. The modal analysis is shortly introduced along with the two mentioned methods. Further, the functionality of tracking-interferometers is discussed as well as the basics for their application in dynamic measurement. One-dimensional measurements using a tracking interferometer are conducted and benchmarked against other devices. Three-dimensional measurements are presented including the necessary coordinate transformation. A small modal analysis is demonstrated. Finally, a measurement strategy for fast modal testing is suggested and additional functionalities required for the tracking interferometer are discussed.