• Title/Summary/Keyword: 주파수 응답

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Calculating Method of FRF with Sub-structure Mode Synthesis Method (부분구조 모드합성법에 의한 주파수응답함수 산출법)

  • Oh, Chang-Guen;Park, Kyung-Il;Park, Sok-Chu
    • Journal of Advanced Marine Engineering and Technology
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    • v.39 no.4
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    • pp.393-398
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    • 2015
  • A very important part in vibration analysis is to calculate the frequency response function (FRF). In general, a large sized or/and complicated structure has many thousands to millions of degrees. Therefore, the FRF cannot be calculated by the traditional analysis method using an inverse matrix. This paper presents a new FRF calculation method of a superstructure by synthesizing sub-structure modes, of which the DOF can be deduced by partitioning into some sub-structures. To confirm its analysis results, the method was applied to an assembled plate ($B300{\times}L900{\times}t5mm$) with three diagonal sub-plates($B300{\times}L300{\times}t5mm$) in series and compared with the measured data. The test results have were comparable those of the calculated ones with an error less than 5%.

Comparison of Projection-Based Model Order Reduction for Frequency Responses (주파수응답에 대한 투영기반 모델차수축소법의 비교)

  • Won, Bo Reum;Han, Jeong Sam
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.38 no.9
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    • pp.933-941
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    • 2014
  • This paper provides a comparison between the Krylov subspace method (KSM) and modal truncation method (MTM), which are typical projection-based model order reduction methods. The frequency responses are compared to determine the numerical accuracies and efficiencies. In order to compare the numerical accuracies of the KSM and MTM, the frequency responses and relative errors according to the order of the reduced model and frequency of interest are studied. Subsequently, a numerical examination shows whether a reduced order can be determined automatically with the help of an error convergence indicator. As for the numerical efficiency, the computation time needed to generate the projection matrix and the solution time to perform a frequency response analysis are compared according to the reduced order. A finite element model for a car suspension is considered as an application example of the numerical comparison.

Characteristic Analysis of Falling Weight Impact Response in CF/Epoxy Composite Plates Using Frequency Responses (주파수 응답을 이용한 CF/Epoxy 복합적층판의 낙추충격 특성평가)

  • 임광희;박노식;김영남;김선규;양인영
    • Composites Research
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    • v.16 no.2
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    • pp.9-17
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    • 2003
  • We have implemented a system of falling weight impact tester in order to evaluate the impact energy absorbing characteristics and impact strength of CFRP laminate plates. The absorbed energy of T-300 orthotropic composites is higher than that of quasi-isotropic specimen over impact energy 7J, but in case of using T700 fiber, much difference does not show. Also, absorbed energy of T-300 orthotropic composites, which are composed of the same stacking number and orientation became more than that of T700 fiber specimen however there was no big difference in case of quasi-isotropic specimens. Delamination area of impacted specimens was measured with ultrasonic C-scanner to find correlation between impact energy and delamination area. Delamination area and frequency responses were evaluated between impacted and unimpacted specimens. There is a strong correlation between frequency responses and impact-induced delamination. The presence and scale of damages have been investigated based on the variations of frequency responses.

Size Optimization of a Rod Using Frequency Response Functions of Substructures (부분 구조의 주파수 응답 함수를 이용한 봉의 치수 최적화)

  • Yoon, Hong Geun;Lee, Jin Woo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.41 no.10
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    • pp.905-913
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    • 2017
  • In this work, a method of size optimization is proposed to maximize the natural frequency of a rod that consists of a hidden shape in one part and an exposed shape in the other. The frequency response function of a rod composed of two parts is predicted by using the frequency response functions of each of the parts instead of the shapes of the parts. The mass and stiffness matrices of the rod are obtained by using the mass and stiffness matrices of the equivalent vibration systems, which are obtained by applying the experimental modal analysis method to the frequency response functions of the parts. Through several numerical examples, the frequency response function obtained by using the proposed method is compared with that of a rod to validate the prediction method based on equivalent vibration systems. A size optimization problem is formulated for maximizing the first natural frequency of a combined rod, which is replaced with an equivalent vibration system, and a rod structure is optimized by using an optimization algorithm.

A Study on the optimum characteristic parameter of Modified CFDN's (Modified CFDN's 특성 파라미터의 최적화에 대한 고찰)

  • Ko Byeong-Seob;Kim Hack-Yoon
    • Proceedings of the Acoustical Society of Korea Conference
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    • pp.223-226
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    • 1999
  • 인공 잔향기를 구현하는데 있어서, 잔향 시스템의 안정도 및 시간-주파수 응답을 용이하게 제어하기 위하여 일반 FDN's(Feedback Delay Networks)에서의 귀환 행렬인 unitary 행렬를 circulant 행렬로 사용한 CFDN's가 최근에 제안되었다. 그러나, 이 구조는 주파수 응답의 평탄도가 낮고, 영점들의 위치를 조절하기 어렵다는 문제점이 있다. 따라서, 본 연구에서는 CFDN's의 시간응답 특성을 최대한 유지하면서 주파수 응답 특성을 개선하기 위하여, 일반 귀환 필터의 귀환부에 직접경로가 없는 CFDN's를 적용한 MCFDN's(Modified CFDN's) 에 관하여 고찰하고, 이 시스템의 특성을 결정하는 특성 파라미터의 최적화에 대하여 고찰하고자 한다.

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A Study on the Characteristics of Frequency Response Functions for Rotor System with Anisotropic Stator and Asymmetric Rotor (비등방 정지부 및 비대칭 회전부를 갖는 회전체의 주파수응답함수 특성에 관한 연구)

  • Han, Dong-Ju
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.33 no.10
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    • pp.42-50
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    • 2005
  • Based upon the derived analytical model and equation of motion for the general rotor system with anisotropic stator and asymmetric rotor treated as a periodically time-varying system, the series of equations are structured by associating with the time modulated coefficients. The frequency response functions (FRFs) expressed by physical parameters are derived in such a convenient way from the direct inverse matrices of the Fourier transformation of those series of equations, from which the characteristics are analyzed and the properties are suggested.

Experimental Researches on the Nonlinear Parameter Identifications and Higher Frequency Response Characteristics of Direct-Radiating Loudspeaker (직접방사형 라우드스피커의 비선형 매개변수 규명 및 고차 주파수 응답특성에 관한 실험연구)

  • 박석태;채장범;홍석윤
    • The Journal of the Acoustical Society of Korea
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    • v.17 no.7
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    • pp.61-73
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    • 1998
  • 라우드스피커의 비선형 음향특성을 해석하기 위하여 라우드스피커 다이아프램의 비 선형특성을 실험적으로 분석하였다. 라우드스피커를 집중질량계로 모델링하고, 출력소음이 없을 때 적용이 가능한 하모닉 발란스법과 출력소음이 있을 때도 적용할 수 있는 통계적 방 법인 라그란지 배수법을 사용하여 비선형 매개변수를 규명하였다. 70Hz 이하의 주파수 영역 에서는 라그란지 배수법이 2차 하모닉 왜곡특성에서 상대적으로 좋은 결과를 보였으며, 3차 하모닉 왜곡특성에서는 하모닉 발란스법이 실험결과와 잘 일치하였다. 전압가진 및 전류 가 진실험을 통하여, 일반화된 주파수 응답함수를 유도하였고 하모닉 왜곡 및 상호변조 특성을 고찰하였다. 고차 주파수 응답특성은 라우드스피커 비선형 매개변수의 변동에 따른 다이아 프램의 비선형특성을 해석하는데 유용한 수단이 될 수 있음도 확인하였다.

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Estimation of frequency response of traveling-wave optical modulator with phase reversal (위상반전 진행파 광변조기에서 주팟응답의 추정)

  • 한영탁;이우진;김창민
    • Korean Journal of Optics and Photonics
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    • v.12 no.4
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    • pp.327-333
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    • 2001
  • Estimation of the frequency response of Ti:LiNb03 traveling-wave optical modulator with phase reversal electrodes is succinctly presented. The fact that such devices may have bandpass characteristics is demonstrated through simulations based on the derived equations. The influence of each parameter of traveling-wave electrodes on the frequency response is investigated in detail. It is shown that the center frequency and the bandwidth of response curves can be effectively adjustable by changing the MW effective index and the interaction length of the electrodes. rodes.

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Optimal Design of IIR Digital Filter Using the Genetic Algorithm (유전자 알고리즘을 이용한 IIR 디지털 필터 최적화)

  • Song, Young-Jun;Kong, Seong-Gon
    • Proceedings of the KIEE Conference
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    • pp.800-802
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    • 1999
  • 본 논문에서는 기존의 알고리즘에서 벗어나 새로이 제안된 유전자 알고리즘을 이용하여 디지털 필터를 설계하는데 목적이 있다. 이 방법은 아날로그 필터에서 디지털 필터로의 전환이 불필요하며, 기존의 디지털 필터 설계방법과는 달리 저역통과(low-pass), 고역통과(high-pass), 대역통과(band-pass), 대역소거(band-stop) 필터와 같은 주파수 선택별 필터를 각각 독립적으로 설계 가능하게 하고, 이에 따른 계산 손실을 줄일 수 있다. 유전자 알고리즘을 사용하는데 있어 적합도 함수는 주파수 응답 크기를 이용한다. 실제로 주파수 응답특성과 디지털 필터의 계수와는 밀접한 관계가 있으므로, 원하는 필터의 주파수응답특성을 통해, 디지털 필터의 계수를 최적화 한다. 또한 필터계수 최적화 과정에 있어, 선택, 교배, 돌연변이와 같은 유전 연산자 적용시 필터의 계수들은 각각 안정도가 보장되어지는 범위내에서 선택되게 한다. 디지털 필터를 설계한 후 기존의 방법과 새로이 제안된 방법의 성능을 비교 평가 한다.

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Convergence Characteristics of the Frequency Response Functions of Non-Linear Systems Expressed in Terms of the Volterra Series (Volterra급수로 나타낸 비선형시스템 주파수응답함수의 수렴특성)

  • ;Tomlinson, G. R.
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.8
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    • pp.1901-1906
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    • 1995
  • The frequency response functions of systems incorporating a non-linear cubic stiffness subject to sinusoidal excitation are derived using the Volterra series and the convergence characteristics investigated. It is shown that the series representation of the frequency response functions converges only when the sinewave input amplitude is within a certain range. Within the range of convergence the frequency response function based on the Volterra series approaches the analytical one as more higher order frequency response function terms are included. Proposed is a criterion for the studies systems to predict approximately the range of sinewave input amplitude for which the series representation of the frequency response functions converges.