• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.351-355
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• 1996

유연한 보의 진동문제에 대해 Filtered-X LMS 알고리즘을 이용하여 제어계를 구성하고 디지탈 신호처리보드를 이용하 여 실시간 제어를 수행하였다. 제어 엑추에이터로는 피에조 세라믹을 사용하였고 정현파 및 백색잡음 형태의 외력으 로 Shaker를 이용하여 보를 가진하였다. 백색잡음가진 실험결과 1차 고유진동수에서 14dB의 진동저감을 할 수 있었 으며 관심 주파수영역내에서진동이 고르게 저감되었다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.6
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• pp.1426-1435
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• 1990

Dynamic behaviour of point tracking system mounted on flying vehicle shaking in a random manner is investigated and the system dynamic is represented by nonlinear stochastic equations. 2-D.O.F. nonlinear stochastic equations are successfully transformed to linear stochastic equations via equivalent linearization procedure in stochastic sense. Newly developed hybrid technique is used to obtain response statistics of the system under non-white random excitation, which is proved to be remarkably accurate one by performing stochastic simulation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1994.10a
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• pp.116-120
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• 1994

최근 항공우주 및 생산자동화 분야의 급격한 발달에 따라 정밀도와 효율성을 향상시키기 위해 저중량, 고강도 구조물이 요구된다. 그러나 경량화 추세로 인해 수반되는 구조물의 유연성 증가로 외력에 대한 구조응답의 진폭이 커지고 구조물의 피로 수명이 단축되어 매우 위험한 상황에 이를 수 있다. 이런 바람직하지 않은 진동현상을 제어하기 위해 여러 제어이론을 응용한 진동억제시스템의 연구가 활발하며, 신소재인 압전재료의 개발로 새로운 방향이 제시되고 있다. 압전재료는 유연한 구조물에 부착되어 압전재료의 수축, 팽창 운동에 의해 발생된 에너지를 부착된 구조물에서의 제어력으로 사용되어, 진동 혹은 자세 및 형상 제어에 활용되고 있다. 압전재료에 대한 연구로는 Crawley, de Luis3가 보의 표면 혹은 내부에 압전세라믹을 부착하여 액튜에이터로 사용하는 경우 집중모멘트를 가하는 역할을 함을 밝혔고, Hanagud, obal은 압전재료를 센서와 액튜에이터로 사용해 복합재료 보에 대한 최적 진동제어 알고리즘을 개발, 그 성능에 대한 효과를 조사하였고 임의의 위치에 부착된 센서 및 액튜에이터를 고려한 복합재료 보의 운동방정식을 유한요소법을 이용 유도하였으며 변위율 피드백(rate feedback)과 모달피드백(modal feedback) 제어기를 적용하여 진동제어 효과를 고찰하였다. 그리고 Tomas, James, Hubbard는 압전필름을 액튜에이터로 사용해 복합재료 보에 Liapunov 제어기와 변위율 피드백 제어기를 사용하여 능동감쇠기를 설계하였고, Lee, Chaing, Sullivan은 압전필름을 센서와 액튜에이터로 사용해 평판에 변위율 피드백 제어기를 적용한 능동감쇠기를 설계하고 실험적으로 수행하였다. Base가 백색잡음가진을 지속적으로 받을 때 보끝의 움직임이 최소가 되도록 제어하고자 연구를 수행 중인 바 그 결과로소 본 논문에서는 적용시켰고 F-P-K 방정식을 이용해 확률영역으로 변환하여 LQR 제어기와 pole allocation 제어기를 시스템에 적용시켜 우수한 특성을 갖음을 제어 시뮬레이션의 결과를 통해 입증하였다.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.37 no.6
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• pp.48-59
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• 2000

Eigendecomposition based direction-of-arrival(DOA) estimation algorithm such as MUSIC(multiple signal classification) is known to perform well and provide high resolution in white noise environment. However, its performance degrades severely when the noise process is not white. In this paper we consider the DOA estimation problem in a colored noise environment as a problem of extracting periodic signals from noise, and we take the problem to the wavelet domain. Covariance matrix of multiscale components which are obtained by taking wavelet decomposition on the noise has a special structure which can be approximated with a banded sparse matrix. Compared with noise the correlation between multiscale components of narrowband signal decays slowly, hence the covariance matrix does not have a banded structure. Based on this fact we propose a DOA estimation algorithm that transforms the covariance matrix into wavelet domain and removes noise components located in specific bands. Simulations have been carried out to analyze the proposed algorithm in colored noise processes with various correlation properties.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.2
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• pp.135-143
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• 2008

In this study, it was investigated for dynamic nonlinear characteristics using dynamic data obtained by shaking table test. The design of Tuned Liquid Damper(TLD) has limitation to plan based on Tuned Mass Damper(TMD) analogy and linear wave theory. Also, while there are many studies regarding properties of TLD under harmonic load, there are not estimated for dynamic non-linear characteristics of TLD under the load that is not governed by particular frequency like a white noise. This paper investigated dynamic non-linear characteristics of TLD varied with load amplitude using a white noise and suggested equations that can estimate damping ratio, natural frequency ratio and effective mass ratio of TLD.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.3
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• pp.301-309
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• 2003

The non linear control algorithm with actuator saturation for a randomly excited oscillator has been widely explored and has shown promising results, but the probabilistic analysis of the algorithm has been rarely made due to its non-linear nature and the fact that the analytical solution of probability density function (PDF) for controlled responses does not exist. In this paper, a method for the probabilistic analysis on the non linear control algorithm with actuator saturation is proposed based on the equivalent non linear system method. Numerical examples are given to verify the approximation solution of PDF comparing to a statistically obtained PDF using a Gaussian white noise and a Kanai - Tagimi filtered Gaussian white noise.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.6
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• pp.28-38
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• 2010

In order to remove the noise contained in recorded analog video, it is important to recognize the real characteristics and strength of the noise. This paper presents an efficient training-based noise reduction method for recorded analog video after analyzing the noise characteristics of analog video captured in a real broadcasting system. First we show that there is non-negligible noise correlation in recorded analog video and describe the limitations of the traditional noise estimation and reduction methods based on additive white Gaussian noise (AWGN) model. In addition, we show that auto-regressive (AR) model considering noise correlation can be successfully utilized to estimate and synthesize the noise contained in the recorded analog video, and the estimated AR parameters are utilized in the training-based noise reduction scheme to reduce the video noise. Experiment results show that the proposed method can be efficiently applied for noise reduction of recorded analog video with non-negligible noise correlation.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.3
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• pp.175-181
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• 2001

An investigation into the response statistics of a spring-pendulum system whose base oscillates randomly along vertical and horizontal line is made. The spring-pendulum system with internal resonance examined is known to be a good model for a variety of engineering systems, including ship motions with nonlinear coupling between pitching and rolling motions. The Fokker-Planck equation is used to generate a general first-order differential equations for the random responses of the system are reduced to a system of autonomous ordinary differential equations. In view of equilibrium solutions of this system and their stability, the response statistics is examined. It is seen that increase in horizontal excitation level leads to a decreased width of the internal resonance region.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.3
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• pp.1-7
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• 2003

Excitation and system identification are carried out for a full-scale five-story structure to obtain fundamental data which will be used for the design of viscoelastic dampers, The hybrid mass driver(HMD) installed on the fifth floor was employed as external exciter to provide excitation for the building, Each floor response was measured and processed to find out where and how the viscoelastic dampers are located and designed. The sine-sweep and white noise loadings were applied to the structure by the HMD to obtain dynamic characteristics such as natural frequencies, damping ratios, and modes, The identified building was experimentally investigated again with the designed viscoelastic dampers installed at inter-stories to obtain the response behavior in the companion paper.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.8
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• pp.850-856
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• 2009

A new type bi-directional damper using a tuned liquid column damper(TLCD) and a tuned sloshing damper(TSD) is introduced in this study. Two dampers are usually needed to reduce wind-induced responses of tall buildings since they are along and across wind ones. The proposed damper has the advantage of controlling both responses with one damper. One of objectives of this study is to derive analytical dynamics to investigate coupled effects due to TLCD and TSD. Another objective is to address the effect of coupled control force due to TLCD and TSD on the dynamic characteristic of the damper based on analytical dynamics. Shaking table test is undertaken to experimentally grasp dynamic characteristics of the damper under white noise excitation. Its dynamic characteristic is expressed by the transfer function from the shaking table acceleration to the control force generated from the damper. Finally, its design parameters are identified based on the coupled dynamics, which include the mass ratio of horizontal liquid column to total liquid for a TLCD, the participation factor of the fundamental liquid sloshing for a TSD and damping ratio for both cases.