Predicting 3D Motions from Single-Camera Optical Test Data
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S.I. : COMPUTER VISION AND SCANNING LASER VIBROMETRY METHODS
Predicting 3D Motions from Single-Camera Optical Test Data D.P. Rohe1
· B.L. Witt1 · T.F. Schoenherr1
Received: 2 April 2020 / Accepted: 4 August 2020 © Sandia National Laboratories 2020
Abstract In a typical optical test, a stereo camera pair is required to measure the three-dimensional motion of a test article; one camera typically only measures motions in the image plane of the camera, and measurements in the out-of-plane direction are missing. Finite element expansion techniques provide a path to estimate responses from a test at unmeasured degrees of freedom. Treating the case of a single camera as a measurement with unmeasured degrees of freedom, a finite element model is used to expand to the missing third dimension of the image data, allowing a full-field, three-dimensional measurement to be obtained from a set of images from a single camera. The key to this technique relies on the mapping of finite element deformations to image deformations, creating a set of mode shape images that are used to filter the response in the image into modal responses. These modal responses are then applied to the finite element model to estimate physical responses at all finite element model degrees of freedom. The mapping from finite element model to image is achieved using synthetic images produced by a rendering software. The technique is applied first to a synthetic deformation image, and then is validated using an experimental set of images. Keywords Optical · Finite element expansion · Synthetic images · Structural dynamics
Introduction Optical techniques are becoming popular due to the fullfield, three-dimensional motions that they can obtain on the surfaces of structures. Traditionally, when 3D motions are desired in a structural dynamics test, a stereo pair of cameras is required to obtain the measurement. A single camera is only able to identify motions in the image plane, and any motions perpendicular to these directions are not captured. In many situations, only one camera may be present during an event, but it would be useful to be able Sandia National Laboratories is a multimission laboratory managed and operated by National Technology, Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DENA0003525. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government. D.P. Rohe
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Sandia National Laboratories, P.O. Box 5800 - MS0557, Albuquerque, NM, 87123, USA
to estimate 3D motions of a structure. Considering the example of a building during an earthquake: there may be cameras throughout the city that have a view of this building, but likely not a well-calibrated stereo pair. Still, engineers would be interested in the defor
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