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  • 1
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    Eigensystem realization algorithm modal identification experiences with mini-mast (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This paper summarizes work performed under a collaborative research effort between the National Aeronautics and Space Administration (NASA) and the German Aerospace Research Establishment (DLR, Deutsche Forschungsanstalt fur Luft- und Raumfahrt). The objective is to develop and demonstrate system identification technology for future large space structures. Recent experiences using the Eigensystem Realization Algorithm (ERA), for modal identification of Mini-Mast, are reported. Mini-Mast is a 20 m long deployable space truss used for structural dynamics and active vibration-control research at the Langley Research Center. A comprehensive analysis of 306 frequency response functions (3 excitation forces and 102 displacement responses) was performed. Emphasis is placed on two topics of current research: (1) gaining an improved understanding of ERA performance characteristics (theory vs. practice); and (2) developing reliable techniques to improve identification results for complex experimental data. Because of nonlinearities and numerous local modes, modal identification of Mini-Mast proved to be surprisingly difficult. Methods were available, ERA, for obtaining detailed, high-confidence results.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-4307 , NAS 1.15:4307
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Rigid body mode identification of the PAH-2 helicopter using the eigensystem realization algorithm (1992)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The rigid body modes of the PAH-2 'Tiger' helicopter were identified using the Eigensystem Realization Algorithm (ERA). This work complements ground vibration tests performed using DLR's traditional phase resonance technique and the ISSPA (Identification of Structural System Parameters) method. Rigid body modal parameters are important for ground resonance prediction. Time-domain data for ERA were obtained by inverse Fourier transformation of frequency response functions measured with stepped-sine excitation. Mode purity (based on the Phase Resonance Criterion) was generally equal to or greater than corresponding results obtained in the ground vibration tests. All identified natural frequencies and mode shapes correlate well with corresponding ground vibration test results. The modal identification approach discussed in this report has become increasingly attractive in recent years due to the steadily declining cost and increased performance of scientific computers. As illustrated in this application, modern time-domain methods can be successfully applied to data acquired using DLR's existing test equipment. Some suggestions are made for future applications of time domain modal identification in this manner.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-107690 , NAS 1.15:107690 , DLR-IB-232-91/J07
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    A consistent-mode indicator for the eigensystem realization algorithm (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A new method is described for assessing the consistency of structural modal parameters identified with the Eigensystem Realization Algorithm. Identification results show varying consistency in practice due to many sources including high modal density, nonlinearity, and inadequate excitation. Consistency is considered to be a reliable indicator of accuracy. The new method is the culmination of many years of experience in developing a practical implementation of the Eigensystem Realization Algorithm. The effectiveness of the method is illustrated using data from NASA Langley's Controls-Structures-Interaction Evolutionary Model.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA PAPER 92-2136 , AIAA Dynamics Specialists Conference; Apr 16, 1992 - Apr 17, 1992; Dallas, TX; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    A consistent-mode indicator for the eigensystem realization algorithm (1992)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A new method is described for assessing the consistency of model parameters identified with the Eigensystem Realization Algorithm (ERA). Identification results show varying consistency in practice due to many sources, including high modal density, nonlinearity, and inadequate excitation. Consistency is considered to be a reliable indicator of accuracy. The new method is the culmination of many years of experience in developing a practical implementation of the Eigensystem Realization Algorithm. The effectiveness of the method is illustrated using data from NASA Langley's Controls-Structures-Interaction Evolutionary Model.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-107607 , NAS 1.15:107607 , Structures, Structural Dynamics, and Materials Conference; Apr 13, 1992 - Apr 17, 1992; Dallas, TX; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Modal identification of a deployable space truss (1990)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Work performed under a collaborative research effort between NASA and the German Aerospace Research Establishment (DLR) is summarized. The objective is to develop and demonstrate advanced technology for system identification of future large space structures. Recent experiences using the eigensystem realization algorithm (ERA) for modal identification of Mini-Mast are reported. Mini-Mast is a 20-meter-long deployable space truss used for structural dynamics and active-vibration control research at the NASA Langley Research Center. Due to nonlinearities and numerous local modes, modal identification of Mini-Mast proved to be surprisingly difficult. Methods available with ERA for obtaining detailed, high-confidence results are illustrated.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-102720 , NAS 1.15:102720 , International Seminar on Modal Analysis and Structural Dynamics; Sep 17, 1990 - Sep 21, 1990; Leuven; Belgium
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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