• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1677-1678
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• 2008

본 논문은 회전기의 비틀림 현상을 억제하기 위하여 복소쌍입력 기술함수 기법을 이용한 제어시스템을 구성한다. 시스템의 주기적 출력은 복소 기술함수로 표현되며 제어기는 이러한 함수를 바탕으로 비선으로 설계된다. 제안한 알고리즘의 타당성 및 성능의 우수성을 검증하기 위하여 2관성 특성을 갖는 DC 전동기 시스템에 적용하여 실시간 실험을 통해 성능을 분석하였다. 시스템을 구동하기 위한 하드웨어 보드는 PSoC(Programmable System on Chip) 프로세서를 이용하여 임베디드 형태로 구성하였으며 실시간 데이터는 제안하는 제어알고리즘이 프로그램되어 있는 PC의 Matlab/Simulink 소프트웨어와 연동이 가능하게 구성하였다.

• Journal of the Korean Society for Railway
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• v.17 no.6
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• pp.397-401
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• 2014

In order to rationally design a new conceptual submerged floating railway, prediction of wave forces applied to the structure is very important. In this paper, equations to calculate such forces based on hydrodynamic theories were proposed and model tests were carried out. Inertia forces and drag forces, calculated using Morison's equation and the linear small amplitude wave theory, were in good agreement with the results from model tests conducted in a wave making tank. Drag forces were negligible compared with inertia forces. Also, wave forces showed linear variation with the changing wave heights. It was revealed that the linear wave theory and Morison's equation can give a simple and useful solution for the prediction of wave forces in the initial design stage of a submerged floating railway.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.4
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• pp.175-184
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• 2006

Two methods of the nonlinear static pushover analysis have been presented for the performance-based seismic design and evaluation of MDOF continuous bridges. Guidelines for buildings presented in FEMA-273 applying the Displacement Coefficient Method (DCM) and in ATC applying the Capacity Spectrum Method(CSM) have been modified for MDOF bridges. Two methods are compared with the time- history analysis. The lateral load distribution pattern for seismic loads has been examined in the static pushover analysis. The force-based fiber frame finite element has been implemented in the modeling of reinforced concrete piers.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.5
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• pp.45-51
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• 2002

The characteristics of nonlinear seismic behavior and failure mechanism of RC space frame in railroad viaducts have been studied by the numerical analysis in time domain. The structure concerned is modeled in 3 dimensional extent and the RC frame elements consisting of fibers are employed for the columns. The fibers are characterized as RC zone and PC one to distinguish the different energy release after cracking resulted from the bond characteristic between concrete and re-bar. Due to the deviation of the mass center and the stiffness center of the entire structure the complex behavior is shown under seismic actions. The excessive shear force is concentrated on the column beside flexible one relatively, which leads to the failure of bridge concerned.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.4 s.70
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• pp.385-393
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• 2005

This paper established the dynamic model of a flexible Timoshenko beam capable of geometrical nonlinearities subject to large overall motions by using the finite element method. Equations of motion are derived by using Hamilton principle and are formulated in terms of finite elements in which the nonlinear constraint equations are adjoined to the system using Lagrange multipliers. The Newmark direct integration method and the Newton-Raphson iteration are employed here for the numerical study which is to demonstrate the efficiency of the proposed formulation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.10a
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• pp.159-163
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• 2001

마찰구동은 다른 구동방식에 비하여 구조가 간단하고, 기계적인 정도를 얻기 쉬우며, 백래쉬 등에 기인하는 비선형 요소인 로스트모션이 없고 관성이 작아 구동력이 작은 이점이 있다. 그 반면에 접촉부에서 미끄럼이 발생하여 큰 구동력을 얻기 어렵고 마찰저항에 의하여 마멸이 생기는 결점이 지적되고 있다. 본 연구에서는 초정밀가공기용 위치결정기구로 마찰구동기구를 사용하기 위하여 위치 결정도에 관한 설계, 구동력의 설계 및 재료의 선택에 관하 여 분석하고 시작품을 제작하여 특성을 연구하였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.1 no.2
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• pp.82-88
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• 1977

1장이 축방향으로 자유로이 움직일 수 있는 단선지시보의 진동에 있어서 그 진폭이 크고, 축방향의 관성력과 전단변형을 고려할때 의 진동을 살폈다. 운동방정식을 처짐을 독립변수로 하는 비선형편미분방정식으로 표시하고, model expansion과 Galerkin 방법에 의해서 비정형연립상미분방정식으로 변형한 다음에 Perturbation method of muthod of multiple scale로 유사해를 구하였다. 또한 보의 진동수-진폭의 관계에 대한 일반적 표현을 구하고, 간단한 구체적 해에 대하여 1차근사해와 진동수-진폭관계를 계산하여 이미 이루어진 연구결과와 비교하였다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.10
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• pp.8-16
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• 2010

An orthogonal frequency division multiplexing (OFDM) system is a special case of multicarrier transmission, where a single data stream is transmitted over a number of lower-rate subcarriers. One of the main reasons to use OFDM is to increase robustness against frequency-selective fading or narrowband interference. However, in the radio systems the distortion introduced by high power amplifiers (HPA's) such as traveling wave tube amplifier (TWTA) considered in this paper, is also critical. Since the signal amplitude of the OFDM system is Rayleigh-distributed, the performance of the OFDM system is significantly degraded by the nonlinearity of the HPA in the OFDM transmitter. In this paper, we propose a simplicial canonical piecewise-linear (SCPWL) model based digital predistorter to compensate for nonlinear distortion introduced by an HPA in an OFDM system. Computer simulation is carried on an OFDM system under additive white Gaussian noise (AWGN) channels with 16-QAM and 64-QAM modulation schemes and modulator/demodulator implemented with 1024-point FFT/IFFT. The simulation results demonstrate that the proposed predistorter achieves significant performance improvement by effectively compensating for the nonlinearity introduced by the HPA.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.12
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• pp.1314-1321
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• 2004

The non-linear responses of a slender rectangular cantilever beam subjected to lateral harmonic base-excitation are investigated by the 2-channel FFT analyzer. Both linear and nonlinear behaviors of the cantilever beam are compared with each other. Bending mode, torsional mode, and transverse mode are coupled in such a way that the energy transfer between them are observed. Especially, superharmonic, subharmonic, and chaotic motions which result from the unstable inertia terms in the transverse mode are analyzed by the FFT analyzer The aim is to give the explanations of the route to chaos, i.e., harmonic motion \longrightarrow superharmonic motion \longrightarrow subharmonic motion \longrightarrow chaos.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.2 s.245
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• pp.171-178
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• 2006

Experimental and theoretical study of the non-planar response motions of a circular cantilever beam subject to base harmonic excitation has been presented in this paper work. Theoretical research is conducted using two non-linear coupled integral-differential equations of motion. These equations contain cubic linearities due do curvature term and inertial term. A combination of the Galerkin procedure and the method of multiple scales are used to construct a first-order uniform expansion for the case of one-to-one resonance. The results show that the non-linear geometric terms are very important for the low-frequency modes of the first and second mode. The non-linear inertia terms are also important for the high-frequency modes. We present the quantitative and qualitative results for non-planar motions of the dynamic behavior.