• 전력전자학회:학술대회논문집
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• 전력전자학회 2020년도 전력전자학술대회
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• pp.160-162
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• 2020

A control technique for the auxiliary buck/boost converter is proposed herein to improve the load transient response of the buck converter. The proposed technique improves the system efficiency by enabling the soft switching operation of the auxiliary converter. The design guidelines for achieving capacitor charge balance for the output capacitor during the transient are also presented herein. The experimental results revealed that the output voltage undershoot and settling time during the load step-up transient were 40 mV and 14 ㎲, respectively, and the output voltage overshoot and settling time during the load step-down transient were 35 mV and 21 ㎲, respectively. The performance and effectiveness of the proposed technique were experimentally verified using a prototype buck converter with a 15-V input, 3.3-V output, and 200-kHz switching frequency.

• Wind and Structures
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• 제15권3호
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• pp.247-261
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• 2012

Some numerical investigations are presented concerning the response of a given plate under turbulence driven excitations. Three different input loads are simulated according to the wall pressure distributions derived from the models proposed by Corcos, Efimtsov and Chase, respectively. Modal solutions (finite element based) are used for building the modal stochastic responses in the sub-critical aerodynamic frequency range. The parametric investigations concern two different values of the structural damping and three values of the boundary layer thickness. A final comparison with available experimental data is also discussed. The results demonstrate that the selection of the adequate TBL input model is still the most critical step in order to get a good prediction.

• 한국전기전자재료학회논문지
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• 제14권8호
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• pp.658-662
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• 2001

This paper describes on the fabrication and characteristics of hot-film type micro-flowsensors integrated with Pt-RTD(resistance thermometer device) and micro-heater on the SOI(Si-on-insulator) membrane and trench structures, in which MGO thin-film was used as medium layer in order to improve adhesion of Pt thin-film to SiO$_2$ layer. Output voltages increased due to increase of heat-loss from sensor to external. The output voltage was 250 nV at N$_2$ flow rate of 2000 sccm/min, heating power of 0.3 W. The response time($\tau$:63%) was about 42 msec when input flow was step-input. The results indicated that micro-flowsensors with the SOI membrane and trench structures have properties of a high-resolution and ow consume power.

• Earthquakes and Structures
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• 제16권1호
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• pp.109-118
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• 2019

This study, analyses the seismic response for a rigid massless square foundation resting on a viscoelastic soil layer limited by rigid bedrock. The foundation is subjected either to externally applied forces or to obliquely incident seismic body or surface harmonic seismic waves P, SV and SH. A 3-D frequency domain BEM formulation in conjunction with the thin layer method (TLM) is adapted here for the solution of elastodynamic problems and used for obtained the seismic response. The mathematical approach is based on the method of integral equations in the frequency domain using the formalism of Green's functions (Kausel and Peck 1982) for layered soil, the impedance functions are calculated by the compatibility condition. In this study, The key step is the characterization of the soil-foundation interaction with the input motion matrix. For each frequency the impedance matrix connects the applied forces to the resulting displacement, and the input motion matrix connects the displacement vector of the foundation to amplitudes of the free field motion. This approach has been applied to analyze the effect of soil-structure interaction on the seismic response of the foundation resting on a viscoelastic soil layer limited by rigid bedrock.

• 드라이브 ㆍ 컨트롤
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• 제13권3호
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• pp.15-23
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• 2016

The direct-drive servo valve(DDV) is a kind of one-stage valve because the main spool valve is directly driven by the dc motor. Since the DDV structure is simple, it is less expensive, more reliable, and offers a reduced internal leakage and a reduced sensitivity to fluid contamination. The control system of the DDV is highly nonlinear due to a current limiter, a voltage limiter, and the flow-force effect on the spool motion. The shape of the step response of the DDV-control system varies considerably according to the magnitudes of the step input and the load pressure. The system-design requirements mean that the overshoots should be less than 20%, and the errors at 0.02s should be less than 2%, regardless of the reference-step input sizes of 1V and 5V and the load-pressure magnitudes of 0MPa and 20.7MPa. To satisfy the system-design requirements, the PID-controller parameters of $K_c$, $T_i$ and $T_d$, and the derivative-feedback gain of $K_{der}$ are designed using the root locus and manual tuning.

• 대한전기학회논문지:전력기술부문A
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• 제51권7호
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• pp.362-370
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• 2002

This paper describes the practical tuning method of dual-input PSS and its application to Muju P/P #2 with Proto PSS, which is based on DSP technology and uses both frequency and power. First, the model parameters of generator system used in this paper have been derived from the generator characteristic testing. Then, in the selection of PSS parameters, the Bode plot is plotted in order to tune the PSS's time constants which are able to compensate the phase lagging due to generator and excitation system. In addition, the eigenvalue analysis is also performed for determining a reliable PSS gain, $K_{s}$. Finally, the transient stability program has been utilized to verify the safe operation of Proto PSS against the predictable disturbances such as the AVR-step test and generator unloading test. In on-site test, the simulated results have been identically duplicated by implementing AVR step test in Muju P/P #2 with Proto PSS, which has the previously designed PSS parameters.s.

• 한국안전학회지
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• 제28권1호
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• pp.158-163
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• 2013

While job stress evaluations are reported in the recent surveys upon the nuclear power plants(NPPs), any significant advance in the types of questionnaires is not currently found. There are limitations to their usefulness as analytic tools for the management of safety resources in NPPs. Data mining(DM) has emerged as one of the key features for data computing and analysis to conduct a survey analysis. There are still limitations to its capability such as dimensionality associated with many survey questions and quality of information. Even though some survey methods may have significant advantages, often these methods do not provide enough evidence of causal relationships and the statistical inferences among a large number of input factors and responses. In order to address these limitations on the data computing and analysis capabilities, we propose an advanced procedure of survey analysis incorporating the DM method into a statistical analysis. The DM method can reduce dimensionality of risk factors, but DM method may not discuss the robustness of solutions, either by considering data preprocesses for outliers and missing values, or by considering uncontrollable noise factors. We propose three steps to address these limitations. The first step shows data mining with response surface method(RSM), to deal with specific situations by creating a new method called response surface data mining(RSDM). The second step follows the RSDM with detailed statistical relationships between the risk factors and the response of interest, and shows the demonstration the proposed RSDM can effectively find significant physical, psycho-social, and environmental risk factors by reducing the dimensionality with the process providing detailed statistical inferences. The final step suggest a robust stress management system which effectively manage job stress of the workers in NPPs as a part of a safety resource management using the surrogate variable concept.

• Journal of Advanced Marine Engineering and Technology
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• 제37권2호
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• pp.205-212
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• 2013

기존 채팅 시스템은 일반적으로 사용자 입력 문장과 데이터베이스 내 목표 문장들 사이의 어휘 일치도에 기반을 둔 방법을 사용한다. 그러나 이러한 방법은 어휘 불일치 문제를 자주 일으킨다. 이러한 문제를 해결하기 위해 순차적으로 적용되는 3단계 문장 검색 방법을 제안한다. 첫 번째 단계는 어휘 수준에서 사용자 입력 문장과 목표 문장들 사이의 공통 키워드 열을 비교하는 것이다. 두 번째 단계는 의미 수준에서 사용자 입력 문장과 데이터베이스 내 문장들 사이의 문장 유형과 의미 표지를 비교하는 것이다. 마지막 단계는 미리 정의된 어휘-구문 패턴을 사용자 입력 문장과 매칭하는 것이다. 실험에서 제안된 방법은 단순 키워드 매칭 방법 보다 더 나은 응답 정확도와 사용자 만족도를 보였다.

• 조명전기설비학회논문지
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• 제24권1호
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• pp.91-97
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• 2010

동역학 행렬 제어(Dynamic Matrix Control) 기법은 각종 산업 현장에서 가장 활발하게 적용되고 있는 고급 제어 기법으로, 최근에는 공정제어의 표준 기법으로 인식되고 있다. 일반적으로 동역학 행렬 제어에서는 대상 플랜트의 거동을 묘사하기 위하여 계단 응답 모델을 이용한다. 본 논문에서는 화력발전의 관류 보일러-터빈 시스템에 동역학 행렬 제어 기법을 적용한 결과를 제시한다. 먼저 제어를 위해 두 개의 입력변수로 스프레이와 댐퍼를 선정한 후, 두 개의 주요 출력 변수에 대한 계단 응답 모델을 생성하였다. 그 후, 생성된 2 입력 - 2 출력 계단 응답 모델을 바탕으로 한, 동역학 행렬 제어의 최적화 계산을 통해 매 순간 보일러 스팀 온도를 제어하는 구조의 제어기를 설계하였다. 제시된 제어기를 두산(주)의 보일러 시뮬레이션 모델인 APESS에 적용한 결과 만족할 만한 제어 성능을 나타냄을 확인하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1986년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 17-18 Oct. 1986
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• pp.393-396
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• 1986

A Sun-Position Sensor using four phototransistors and shadow band device has been designed, and a Sun-Tracking System which tracks varying positions of the sun in elevation and azimuth axes has been built and its performance has been analyzed on the basis of indoor experiments and computer simulations. Two permanent-magnetic Step Motors (1.8.deg./step) for the main actuators and a CRC-800A kit with the Z-80CPU for the main controller have been selected to construct the Sun-Tracking System. It has been shown that the Sun-Position Sensor has about 0.5.deg. resolution and 25msec is required for the response of a single step input to reach its steady state.