The Experts below are selected from a list of 46617 Experts worldwide ranked by ideXlab platform
Hae Sung Lee - One of the best experts on this subject based on the ideXlab platform.
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Damping estimates from reconstructed displacement for low-frequency dominant structures
Mechanical Systems and Signal Processing, 2020Co-Authors: Sunjoong Kim, Kwang-yeun Park, Ho-kyung Kim, Hae Sung LeeAbstract:Abstract This paper proposes a new concept for the estimation of modal damping ratios. This new concept is based on an operational modal analysis (OMA) technique that uses dynamic displacement reconstructed from Measured Acceleration. The reconstructed displacement physically suppresses the high-mode components in Measured Acceleration data and leads to modal participant factors that are sequentially arranged from low- to high-frequency modes. Thus, compared with the conventional approach that utilizes Acceleration data, the proposed procedure provides a more reliable and robust damping estimate regardless of the model order selection. Furthermore, the use of reconstructed displacement guarantees the equilibrium of the system all the time. The OMA adopts a natural excitation technique (NExT) combined with an eigensystem realization algorithm (ERA). A finite element method (FEM)-based finite impulse response filter is adopted to reconstruct the dynamic displacement. The effectiveness and accuracy of the proposed approach is demonstrated for low-frequency dominant structures by using the numerical simulation study of a 9-story shear building and an actual field test of a cable-stayed bridge under operation in Korea. These examples allow a comparison of modal damping ratio estimates using reconstructed displacement and Accelerations.
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Design of an FIR filter for the displacement reconstruction using Measured Acceleration in low‐frequency dominant structures
International Journal for Numerical Methods in Engineering, 2009Co-Authors: Hae Sung Lee, Yun Hwa Hong, Hyun Woo ParkAbstract:This paper presents a new class of displacement reconstruction scheme using only Acceleration Measured from a structure. For a given set of Acceleration data, the reconstruction problem is formulated as a boundary value problem in which the Acceleration is approximated by the second-order central finite difference of displacement. The displacement is reconstructed by minimizing the least-squared errors between Measured and approximated Acceleration within a finite time interval. An overlapping time window is introduced to improve the accuracy of the reconstructed displacement. The displacement reconstruction problem becomes ill-posed because the boundary conditions at both ends of each time window are not known a priori. Furthermore, random noise in Measured Acceleration causes physically inadmissible errors in the reconstructed displacement. A Tikhonov regularization scheme is adopted to alleviate the ill-posedness. It is shown that the proposed method is equivalent to an FIR filter designed in the time domain. The fundamental characteristics of the proposed method are presented in the frequency domain using the transfer function and the accuracy function. The validity of the proposed method is demonstrated by a numerical example, a laboratory experiment and a field test. Copyright © 2009 John Wiley & Sons, Ltd.
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Structural system identification in time domain using Measured Acceleration
Journal of Sound and Vibration, 2005Co-Authors: Joo Sung Kang, Seung-keun Park, Soobong Shin, Hae Sung LeeAbstract:This paper presents a system identification scheme in time domain to estimate stiffness and damping parameters of a structure using Measured Acceleration. An error function is defined as the time integral of the least-squared errors between Measured Accelerations and calculated Accelerations by a numerical model of a structure. To alleviate the ill-posedness of SI problems a regularization technique is employed and a new regularization function for the time-domain SI is proposed. The regularization factor is determined by the geometric mean scheme. The validity of the proposed method is demonstrated by a numerical simulation study on a two-span truss bridge and by an experimental laboratory study on a three-story shear building model.
Giammarco Veruggio - One of the best experts on this subject based on the ideXlab platform.
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Motion estimation and modeling of the environment for underwater vehicles
International Journal of Systems Science, 1998Co-Authors: Roberto Cristi, Massimo Caccia, Giammarco VeruggioAbstract:The problem of localizing an underwater vehicle in a structured environment using sonar returns and Measured Acceleration is addressed. In particular the environment is modeled as a sequence of segments with constant orientation. The combined estimation of the vehicle motion and the orientation of the segments is obtained using an extended Kalman filter based on a suitable state-space model. Several experiments in the test tank show the effectiveness of this technique.
Hyun Woo Park - One of the best experts on this subject based on the ideXlab platform.
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design of an fir filter for the displacement reconstruction using Measured Acceleration in low frequency dominant structures
International Journal for Numerical Methods in Engineering, 2010Co-Authors: Yun Hwa Hong, Hyun Woo ParkAbstract:This paper presents a new class of displacement reconstruction scheme using only Acceleration Measured from a structure. For a given set of Acceleration data, the reconstruction problem is formulated as a boundary value problem in which the Acceleration is approximated by the second-order central finite difference of displacement. The displacement is reconstructed by minimizing the least-squared errors between Measured and approximated Acceleration within a finite time interval. An overlapping time window is introduced to improve the accuracy of the reconstructed displacement. The displacement reconstruction problem becomes ill-posed because the boundary conditions at both ends of each time window are not known a priori. Furthermore, random noise in Measured Acceleration causes physically inadmissible errors in the reconstructed displacement. A Tikhonov regularization scheme is adopted to alleviate the ill-posedness. It is shown that the proposed method is equivalent to an FIR filter designed in the time domain. The fundamental characteristics of the proposed method are presented in the frequency domain using the transfer function and the accuracy function. The validity of the proposed method is demonstrated by a numerical example, a laboratory experiment and a field test. Copyright © 2009 John Wiley & Sons, Ltd.
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Design of an FIR filter for the displacement reconstruction using Measured Acceleration in low‐frequency dominant structures
International Journal for Numerical Methods in Engineering, 2009Co-Authors: Hae Sung Lee, Yun Hwa Hong, Hyun Woo ParkAbstract:This paper presents a new class of displacement reconstruction scheme using only Acceleration Measured from a structure. For a given set of Acceleration data, the reconstruction problem is formulated as a boundary value problem in which the Acceleration is approximated by the second-order central finite difference of displacement. The displacement is reconstructed by minimizing the least-squared errors between Measured and approximated Acceleration within a finite time interval. An overlapping time window is introduced to improve the accuracy of the reconstructed displacement. The displacement reconstruction problem becomes ill-posed because the boundary conditions at both ends of each time window are not known a priori. Furthermore, random noise in Measured Acceleration causes physically inadmissible errors in the reconstructed displacement. A Tikhonov regularization scheme is adopted to alleviate the ill-posedness. It is shown that the proposed method is equivalent to an FIR filter designed in the time domain. The fundamental characteristics of the proposed method are presented in the frequency domain using the transfer function and the accuracy function. The validity of the proposed method is demonstrated by a numerical example, a laboratory experiment and a field test. Copyright © 2009 John Wiley & Sons, Ltd.
J. F. Doyle - One of the best experts on this subject based on the ideXlab platform.
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Combining spectral super-elements, genetic algorithms, and massive parallelism for computationally efficient flaw detection in complex structures
Computational Mechanics, 1997Co-Authors: L. E. Kannal, J. F. DoyleAbstract:An iterative method to determine the location and size of flaws using dynamic response measurements is presented. The solution procedure combines frequency-domain problem solving methods (deconvolution and the spectral element method) with a stochastic iterative search technique based on a genetic algorithm. Experimentally Measured Acceleration and strain responses from example structures are used to verify the method.
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Impact force identification from wave propagation responses
International Journal of Impact Engineering, 1996Co-Authors: M.t. Martin, J. F. DoyleAbstract:The inverse problem of solving for the impact force history using experimentally Measured structural responses tends to be ill-conditioned. This paper uses a frequency domain deconvolution method to help clarify some of the fundamental difficulties and issues involved in this problem. Force reconstructions obtained using experimentally Measured Acceleration responses from four example structures are used to illustrate the points.
Roberto Cristi - One of the best experts on this subject based on the ideXlab platform.
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Motion estimation and modeling of the environment for underwater vehicles
International Journal of Systems Science, 1998Co-Authors: Roberto Cristi, Massimo Caccia, Giammarco VeruggioAbstract:The problem of localizing an underwater vehicle in a structured environment using sonar returns and Measured Acceleration is addressed. In particular the environment is modeled as a sequence of segments with constant orientation. The combined estimation of the vehicle motion and the orientation of the segments is obtained using an extended Kalman filter based on a suitable state-space model. Several experiments in the test tank show the effectiveness of this technique.