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    Membrane Vibration Analysis Above the Nyquist Limit with Fluorescence Videogrammetry (2004)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: A new method for generating photogrammetric targets by projecting an array of laser beams onto a membrane doped with fluorescent laser dye has recently been developed. In this paper we review this new fluorescence based technique, then proceed to show how it can be used for dynamic measurements, and how a short pulsed (10 ns) laser allows the measurement of vibration modes at frequencies several times the sampling frequency. In addition, we present experimental results showing the determination of fundamental and harmonic vibration modes of a drum style dye-doped polymer membrane tautly mounted on a 12-inch circular hoop and excited with 30 Hz and 62 Hz sinusoidal acoustic waves. The projected laser dot pattern was generated by passing the beam from a pulsed Nd:YAG laser though a diffractive optical element, and the resulting fluorescence was imaged with three digital video cameras, all of which were synchronized with a pulse and delay generator. Although the video cameras are capable of 240 Hz frame rates, the laser s output was limited to 30 Hz and below. Consequently, aliasing techniques were used to allow the measurement of vibration modes up to 186 Hz with a Nyquist limit of less than 15 Hz.
    Schlagwort(e): Instrumentation and Photography
    Materialart: SEM X International Congress and Exposition on Experimental and Applied Mechanics; Jun 07, 2004 - Jun 10, 2004; Costa Mesa, CA; United States
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 2
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    Photogrammetry Methodology Development for Gossamer Spacecraft Structures (2002)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Photogrammetry--the science of calculating 3D object coordinates from images-is a flexible and robust approach for measuring the static and dynamic characteristics of future ultralightweight and inflatable space structures (a.k.a., Gossamer structures), such as large membrane reflectors, solar sails, and thin-film solar arrays. Shape and dynamic measurements are required to validate new structural modeling techniques and corresponding analytical models for these unconventional systems. This paper summarizes experiences at NASA Langley Research Center over the past three years to develop or adapt photogrammetry methods for the specific problem of measuring Gossamer space structures. Turnkey industrial photogrammetry systems were not considered a cost-effective choice for this basic research effort because of their high purchase and maintenance costs. Instead, this research uses mainly off-the-shelf digital-camera and software technologies that are affordable to most organizations and provide acceptable accuracy.
    Schlagwort(e): Instrumentation and Photography
    Materialart: AIAA Paper 2002-1375 , 43rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference; Apr 22, 2002 - Apr 25, 2002; Denver, CO; United States|3rd AIAA Gossamer Spacecraft Forum; Apr 22, 2002 - Apr 25, 2002; Denver, CO; United States
    Format: application/pdf
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    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 3
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    Dot Projection Photogrammetric Technique for Shape Measurements of Aerospace Test Articles (2002)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Results from initial laboratory investigations with the dot projection photogrammetric technique are presented for three wind-tunnel test articles with a range of surface scattering and reflection properties. These test articles are a semispan model and a micro air vehicle with a latex wing that are both diffusely reflecting, and a highly polished specularly reflecting model used for high Reynolds number testing. Results using both white light and laser illumination are presented. Some of the advantages and limitations of the dot projection technique are discussed. Although a desirable final outcome of this research effort is the characterization of dynamic behavior, only static laboratory results are presented in this preliminary effort.
    Schlagwort(e): Instrumentation and Photography
    Materialart: AIAA Paper 2002-0532 , 40th AIAA Applied Aerodynamics Conference; Jan 14, 2002 - Jan 17, 2002; Reno, NV; United States
    Format: application/pdf
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  • 4
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    Laser Induced Fluorescence for Photogrammetric Measurement of Transparent or Reflective Aerospace Structures (2003)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: To support the requirement for non- contacting measurement of polymer membrane structures a new technique based on the principles of photogrammetry has been developed and is described here.
    Schlagwort(e): Instrumentation and Photography
    Materialart: 49th Annual International Instrumentation Symposium (ISA); May 04, 2003 - May 08, 2003; Orlando, FL; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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