title: Measurement of 3-D Vibrational Motion by Dynamic Photogrammetry Using Least-Square Image Matching for Sub-Pixel Targeting to Improve Accuracy.
abstract: This paper deals with an improved methodology to measure three-dimensional dynamic displacements of a structure by digital close-range photogrammetry. A series of stereo images of a vibrating structure installed with targets are taken at specified intervals by using two daily-use cameras. A new methodology is proposed to accurately trace the spatial displacement of each target in three-dimensional space. This method combines the correlation and the least-square image matching so that the sub-pixel targeting can be obtained to increase the measurement accuracy. Collinearity and space resection theory are used to determine the interior and exterior orientation parameters. To verify the proposed method, experiments have been performed to measure displacements of a cantilevered beam excited by an electrodynamic shaker, which is vibrating in a complex configuration with mixed bending and torsional motions simultaneously with multiple frequencies. The results by the present method showed good agreement with the measurement by two laser displacement sensors. The proposed methodology only requires inexpensive daily-use cameras, and can remotely detect the dynamic displacement of a structure vibrating in a complex three-dimensional defection shape up to sub-pixel accuracy. It has abundant potential applications to various fields, e.g., remote vibration monitoring of an inaccessible or dangerous facility.
authors.affiliation: Department of Civil Engineering, Sunchon National University, Sunchon 57922, Korea. hslee@sunchon.ac.kr.
authors.forename: Hyoseong
authors.initials: H
authors.lastname: Lee
authors.affiliation: Department of Mechanical &amp; Aerospace Engineering, Sunchon National University, Sunchon 57922, Korea. hnrhee@sunchon.ac.kr.
authors.forename: Huinam
authors.initials: H
authors.lastname: Rhee
authors.affiliation: Department of Civil Engineering, Chonnam National University, Gwangju 61186, Korea. ojh@chonnam.ac.kr.
authors.forename: Jae Hong
authors.initials: JH
authors.lastname: Oh
authors.affiliation: Nuclear Technology Convergence Division, Korea Atomic Energy Research Institute, Daejeon 34057, Korea. pjh213@kaeri.re.kr.
authors.forename: Jin Ho
authors.initials: JH
authors.lastname: Park
keywords: 3-D vibration; correlation matching; digital close-range photogrammetry; displacement sensor; least square matching; sub-pixel targeting