Proceedings ArticleDOI
Modal identification of a rotating-blade system
TLDR
In this paper, a new testing technique and the Ibrahim time-domain (ITD) modal identification algorithm have been combined, resulting in a capability to estimate modal parameters for rotating-blade systems.Abstract:Â
A new testing technique and the Ibrahim time-domain (ITD) modal identification algorithm have been combined, resulting in a capability to estimate modal parameters for rotating-blade systems. This capability has been evaluated on the Sandia two-meter, vertical-axis wind turbine. Variation in modal frequencies as a function of rotation speed has been experimentally determined from 0 rpm (parked) to 800 rpm. Excitation of the rotating turbine was provided by a scheme which suddenly released a pretensioned cable, thus plucking the turbine as it rotated. The structural response was obtained by passing the signals through slip rings. Using the measured free-decay responses as input data for the ITD algorithm, the modes of the rotating turbine were determined at seven rotation speeds. The measured modal parameters were compared with analytical results obtained from a finite element analysis and with experimental results obtained from a complex exponential identification algorithm.read more
Citations
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Book
Vibration of Axially-Loaded Structures
TL;DR: In this paper, a variety of structural components are analyzed with a view to predicting their response to various (primarily axial) loading conditions, and the authors present methods by which the combined effects of vibration and buckling on various structures can be assessed.
Dissertation
Dynamics Modeling and Periodic Control of Horizontal-Axis Wind Turbines
TL;DR: In this article, a state-space modeling, modal analysis, and multi-objective controllers for wind turbines are explored for mitigating loads for these very large, dynamically soft and highly integrated power systems.
Journal ArticleDOI
Floquet Modal Analysis of a Teetered-Rotor Wind Turbine
TL;DR: In this article, the authors examined the operating modes of a two-bladed wind turbine structural model and found that the turbine modes become more dominated by the centrifugal and gyroscopic effects as the rotor speed increases.
Journal ArticleDOI
Damping measurements using operational data
TL;DR: In this paper, the authors measured modal damping using strain-gauge data from an operating wind turbine and verified the method by extracting damping values from an analytically generated data set.
Journal ArticleDOI
An upper hessenberg sparse matrix algorithm for modal identification on minicomputers
TL;DR: The direct use of an upper Hessenberg matrix eliminates the need of transforming a full matrix to such a form and consequently greatly reduces the computational requirements when the QR algorithm is used for the eigensolution.
References
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A method for the direct identification of vibration parameters from the free response
S. R. Ibrahim,E. C. Mikulcik +1 more
Journal ArticleDOI
Random Decrement Technique for Modal Identification of Structures
TL;DR: In this paper, the free responses of a linear structure from its random responses, due to some unknown or known random input or inputs, using the random decrement technique without changing time correlation between signals.
Journal ArticleDOI
A Mathematical Basis for the Random Decrement Vibration Signature Analysis Technique
TL;DR: For the particular case of a linear time invariant system excited by a zero-mean, stationary, Gaussian random process, a Randomdec signature of the output is shown to be proportional to the auto-correlation of theoutput.
Journal ArticleDOI
Free-Vibration Analysis of Rotating Beams by a Variable-Order Finite-Element Method
TL;DR: In this article, the free vibration of rotating beams is analyzed by means of a finite-element method of variable order, where the displacement is assumed to be analytic within an element and thus can be approximated to any degree of accuracy desired by a complete power series.
Journal ArticleDOI
Vibration of a rotating beam with tip mass
TL;DR: In this article, the effects of the root radius, the setting angle and the tip mass are incorporated into the finite element model to investigate the vibration frequency of a rotating beam with tip mass.