Random Decrement Technique for Modal Identification of Structures

Ibrahim, S. R.

doi:10.2514/3.57251

Cited by 308 publications

(134 citation statements)

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“…This has proven to be the case with the most recent studies; however the assessments are not 7 complete at this time. Another technique that has been used is similar situations with reasonable results is the Random Decrement technique [13,14]. This technique does produce correlation-type functions but the triggering process inherent in this approach may reduce the effects of the underlying modal excitations.…”

Section: Use Of Multiple Correlation Calculations To Reduce Beatingmentioning

confidence: 99%

“…Hence a major activity involved the development of individual modules to implement a single technique for integration into the MIDOS framework. The techniques currently developed, in development, or under consideration include: correlation function processing [1,2], Stochastic Subspace Identification (SSI) [3], Frequency Domain Decomposition (FDD) [4], wavelet processing [5], Hilbert-Huang [6], force reconstruction [7,8] as well as other supporting techniques such as mode shape extraction [9], harmonic removal [10], Maximum Entropy Method (MEM) [11,12], random decrement [13,14], etc. Currently, there are limited modules built for standard OMA processing as well as unsteady launch processing based on correlation functions.…”

Section: Module Developmentmentioning

confidence: 99%

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Operational Analysis in the Launch Environment

James

Kaouk

Cao

et al. 2012

Topics in Modal Analysis I, Volume 5

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The launch environment is a challenging regime to work due to changing system dynamics, changing environmental loading, joint compression loads that cannot be easily applied on the ground, and control effects. Operational testing is one of the few feasible approaches to capture system level dynamics since ground testing cannot reproduce all of these conditions easily. However, the most successful applications of Operational Modal Testing involve systems with good stationarity and long data acquisition times. This paper covers an ongoing effort to understand the launch environment and the utility of current operational modal tools. This work is expected to produce a collection of operational tools that can be applied to non-stationary launch environment, experience dealing with launch data, and an expanding database of flight parameters such as damping. This paper reports on recent efforts to build a software framework for the data processing utilizing existing and specialty tools; understand the limits of current tools; assess a wider variety of current tools; and expand the experience with additional datasets as well as to begin to address issues raised in earlier launch analysis studies. INTRODUCTIONThe spacecraft launch environment is a highly complex and non-stationary event that is characterized by high amplitude input forces, highly variable loads, a wide spectrum of responses, constantly changing vehicle mass, active control interactions, staging, and limited instrumentation. At the same time, structural response analyses and loads estimations must be performed with models that are only partially validated using ground test data due to the fact that access to diagnostic and environmental ground tests are limited. To compound matters, projects are tending to use reduced uncertainty factors designed to protect for loads increases and model unknowns. As a result, the designs progress rapidly before loads and structural problems are uncovered. This means that there are very few tools available to recover from structural dynamics issues in such a dynamic environment without costly redesigns late in the design cycle or in early operations.

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Section: Use Of Multiple Correlation Calculations To Reduce Beatingmentioning

confidence: 99%

Section: Module Developmentmentioning

confidence: 99%

Operational Analysis in the Launch Environment

James

Kaouk

Cao

et al. 2012

Topics in Modal Analysis I, Volume 5

View full text Add to dashboard Cite

show abstract

“…By averaging the mean-centred measured outputs subject to a threshold condition, the responses due to the random and step components average to zero leaving an estimate of the impulse response [60]. One drawback of this method is that this decomposition is only strictly valid in the case of a stochastic input, however mathematical proof in [61] shows that the RD can be used to estimate correlation functions when the input is not strictly stochastic.…”

Section: Ii) Random Decrementmentioning

confidence: 99%

Comparative review of methods for stability monitoring in electrical power systems and vibrating structures

Thambirajah

Barocio

Thornhill

2010

IET Gener. Transm. Distrib.

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“…The overdetermined equation (12) is solved by using the least squares method to obtain all the residues. Then, the system poles can be obtained based on the above residues and equation (10). Modal shape, mass, stiffness, damping ratio, and so on are identified according to the relationship among the modal parameters.…”

Section: Theory Of Modal Testmentioning

confidence: 99%

“…The random decrement method is a single-channel signal, which cannot be directly used for modal parameter identification. 9 Using the response signal in time domain, Ibrahim 10 put this technology into the field of multi-channel signals. With the development of the modal analysis technology, Ibrahim time domain (ITD) identification was put forward.…”

Section: Introductionmentioning

confidence: 99%

Modal analysis of a truck cab using the least squares complex exponent test method

Fan

Wang

Zhao

2015

Advances in Mechanical Engineering

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This article introduces the basic theory of modal analysis. The modal testing system is established for a developing truck body. Using a pseudo-random excitation signal along the x, y, and z directions, the modal test is carried out to obtain the dynamic performance by multi-point excitations. The transfer function set is obtained by averaging all transfer functions, and the set is processed by order selection to get 28 order modes. Fitting modal parameters and normalizing modal mass can gain natural frequencies and vibration modes of cab. Then, the modal analysis of truck cab is calculated based on the finite element method, and the results are compared with the test results. The improved measures are put forward to enhance the local stiffness, avoid modal coupling, and reduce vibration noise. So, this article supplies a reference for the dynamic test for the large body.

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Random Decrement Technique for Modal Identification of Structures

Cited by 308 publications

References 0 publications

Operational Analysis in the Launch Environment

Operational Analysis in the Launch Environment

Comparative review of methods for stability monitoring in electrical power systems and vibrating structures

Modal analysis of a truck cab using the least squares complex exponent test method

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