• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1997.11a
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• pp.33-34
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• 1997

장비나 부품이 비행 또는 수송 등 실제상황에서 겪게되는 진동환경에 얼마만큼 견디는지 여부를 확인하고, 예상되는 동적 하중에 의한 성능저하나 오 동작이 일어나지 알는지 확인하기 위해 환경진동시험(environmental vibration test)이 수행된다. 이러한 환경진동시험의 경우에는 대형(대용량)의 진동시험기(shaker 또는 exciter)가 이용되며 진동시험기로부터 에너지를 시험물에 기계적으로 전달시켜줄 수 있는 진동 시험치구(이하, "치구(fixture)")가 필요하게 된다. 따라서 치구의 설계문제가 대두되며, 환경진동시험의 성공여부를 좌우하는데 대단히 중요한 역할을 하게 된다. 치구의 설계시 가장 중요한 점은 시험규격에 정해진 기준스펙트럼(specified reference spectrum)이 치구 위에 설치될 여러 시험물부착점들에 그대로 전달될 수 있는 강체치구(rigid fixture)를 설계하는 것이 가장 이상적이지만 치구의 공진 및 반공진 특성으로 인해 시험물부착점들 마다 스펙트럼이 달라지게 된다. 따라서 시험물은 과대시험(overtest) 또는/그리고 과소시험(undertest)를 겪게된다.최근의 진동시험제어 기법으로서는 다채널시스템을 이용한 여러 시험부착점들에서의 진동레벨의 평균을 제어하는 평균제어기법(average control technique)이 이용되므로서 시험주파수 범위에서 공진진동수(resonance frequency)들은 기준스펙트럼과 동일하게 제어가 가능하나 반공진 진동수(antiresonance frequency)들에서는 반공진 진동수들이 갖는 물리적 특성으로 인해 기준스펙트럼과 동일하게 제어가 이루어지지 않으므로시험규격에 정해진 정확한 진동시험이 수행되지 못하게된다.본 연구에서는 치구의 설계단계에서 치구 위의 여러 시험물 부착점들- 평균제어점(average control points)- 에서의 반공진 진동수들을 고려하여 그 감도를 게산하고, 치구의 구조변경을 수행하여 시험물 부착점들에서의 반공진 진동수를 일치시키므로서 종래의 진동시험제어시 나타나는 반공진진동수에서의 문제점을 제거할 수 있고, 그 결과 시험물 부착점들에서의 스펙트럼이 시험규격에 정해진 스펙트럼대로 진동시험이 수행될 수 있게 하는데 있다.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.156-157
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• 2017

본 논문은 전차원 자속 관측기를 이용한 대용량 매입형 영구자석 동기전동기(IPMSM)의 센서리스 제어 기법을 제안한다. 기존의 전차원 자속 관측기를 사용한 제어 방식은 IPMSM의 자속 모델을 표면 부착형 영구자석 동기전동기(SPMSM)의 자속 모델처럼 해석하기 때문에 추정되는 회전각의 오차가 발생한다. 특히 릴럭턴스 토크가 큰 대용량 IPMSM 구동 시에는 회전각 오차가 크게 나타나므로 단위 전류당 발생하는 최대토크를 감소시켜 정밀한 MTPA 제어가 불가능하다. 제안하는 알고리즘은 전차원 자속 관측기를 통해 추정된 회전각의 오차를 보상하여 대용량 IPMSM의 정밀한 센서리스 제어를 가능하게 한다. 제안하는 기법의 타당성은 시뮬레이션을 통해 확인하였으며, 기존의 알고리즘과 비교하였다.

• Journal of the Korea Concrete Institute
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• v.24 no.1
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• pp.79-86
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• 2012

Though steel reinforcing bars are the most widely used tensile reinforcement, corrosion problems are encountered due to the exposure to aggressive environments. As an alternative material to steel, the fiber reinforced polymers have been used as reinforcement in concrete structures. However, bond strength of FRP rebar is relatively low compared to steel rebar. It has been reported that fibers in matrix can resist crack growth, propagation and finally result in an increase of toughness. In this study, high-strength concrete reinforced with structural fibers was produced to enhance interfacial bond behavior between FRP rebar and concrete matrix. The interfacial bond-behaviors were investigated from a direct pullout test. The test variables were surface conditions of GFRP bars and fiber types. Total of 54 pullout specimens with three different types of bars were cast for bond strength tests. The bond strength-slip responses and resistance of the bond failure were evaluated. The test results showed that the bond strength and toughness increased according to the increased fiber volume.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.16 no.1
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• pp.1-9
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• 2004

In this study, several new types of floating breakwater are proposed according to the geometry of the vertical barrier and the existence of horizontal plate, and are compared to the steel floating breakwater adopted in Won-Jun fishing port and the performance of wave control is numerically investigated by using Green function method. From the numerical results, model attached the horizontal barrier under the vertical barrier is more efficient for reflection and transmission coefficient than the steel floating breakwater in Won-Jun fishing port. It is confirmed that the transmitted waves can be controlled efficiently by optimizing the length and distance of a vertical and horizontal barriers.

• Tunnel and Underground Space
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• v.32 no.6
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• pp.353-362
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• 2022

The wet shotcrete refers to a method in which all materials are mixed and then supplied to the spraying device, compressed air is added to the nozzle, and the spraying speed is improved to spray on the target surface. In order to reproduce the amount of shotcrete used in the wet method in the field and the situation at the laboratory scale, it is essential to control the discharge amount of the equipment. In this study, in order to increase the reproducibility of field conditions at the laboratory scale, a flow control system for shotcrete mortar spraying equipment was developed and applied to the equipment. To verify the developed equipment, a discharge control test using water and mortar was performed. In the developed control system, the discharge was smoothly controlled according to the user input value for the mono pump, but the discharge was not properly controlled according to the input value for the screw pump because of a reducer. When a speed reducer is attached, it is necessary to adjust the operation rate of the screw pump close to the target flow rate by increasing the operation rate of the screw pump while lowering the operation rate of the mono pump.

• Journal of the Korean Institute of Intelligent Systems
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• v.17 no.6
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• pp.738-743
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• 2007

In this paper, a muscle motion sensing system and an artificial arm control system are studied. The artificial arm is for the people who lost one's forearm. The muscle motion sensing system detect the intention of motion from the upper arm's muscle. In sensing system we use flex sensors which is electrical resistance type sensor. The sensor is attached on the biceps brachii muscle and coracobrachialis muscle of the upper arm. We propose an algorithm to classify the one's intention of motions from the sensor signal. Using this algorithm, we extract the 4 motions which are flexion and extension of the forearm, pronation and supination of the arm. To verify the validity of the proposed algorithms we made experiments with two d.o.f. artificial arm. To reduce the control errors of the artificial arm we also proposed a fuzzy PID control algorithm which based on the errors and error rate.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.454-459
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• 2017

In this study, a thermal system was designed using a 3-way valve and PTC attached to a solar module. This design could help solve the problem of rising fossil fuel costs caused by limited reserves and environmental problems resulting from fossil fuel use. The thermal system is a hot-air and heating control system composed of a temperature sensor part, mode setting part (for hot air and heating modes), supply part, and thermal system control part. The temperature sensor part has piping and an indoor temperature display, and the temperature setting part has multiple monitoring functions. The mode setting part switches between hot air and heating modes and can be used to set the temperature. The thermal system control part performs functions such as PTC control and temperature setting, PTC day and night and time selection, hot air and heating control, and three-way valve selection. The results verify that the system operates with stable response speeds of $680{\mu}s$ in the temperature sensor part, $700{\mu}s$ in the mode setting part, and $610{\mu}s$ in the thermal system control part.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.6
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• pp.507-514
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• 1999

한국전력에서는 인천화력 4호기 수명연장의 일환으로 여자시스템 교체가 이루어졌다. 기존의 회전형 여자 시스템은 발전기축에 부여자기와 교류여자기가 부착되어 회전하는 형태로 과거 스위칭소자 용량의 한계를 극복하기 위하여 설계된 시스템으로 전력연구원에는 회전형 여자시스템을 새롭게 개발된 아날로그와 디지털의 하이브리드 제어기와 대용량 사이리스터 제어정류기를 가지고 잇는 정지형 이중화 여자시스템으로 교체하였다. 설비의 신뢰성을 높이기 위하여 정지형 여자시스템의 상태를 순시 감시하기 위한 데이터 취득 시스템이 설치 되었고 위상제어정류기는 운전시 1대가 고장이 발생하더라도 발전기의 전부하 능력을 유지하기 위하여 3대가 병렬로 운전되는 N+1 방식을 채택하였다. 시스템의 신뢰성 시험은 성능평가를 위한 시운전시에 검증되었으며 성공적으로 운전중에 있다.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.3
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• pp.20-28
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• 2000

Air wiping technique is widely used because of easy and efficient coating control in present CGL The coating weight is controlled by nozzle header pressure. strip line speed, and the distance between strip and nozzle. Coating defects are resulted from the unbalance of these control factors and the inaccuracy of coating equipments. We investigates the main cause of coating defects, such as edge overcoating and coating deviation through various experiments. It is found that the edge overcoating is mainly come from nozzle lip type, and the coating deviation is caused by the unbalance of dynamic pressure.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.9
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• pp.55-63
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• 2003

An attitude control system using reaction thrusters for the upper stage of a launch vehicle is considered. The thruster configuration (position and direction) determines control system response, fuel consumption, effective torque and system fault tolerance. We propose a procedure for finding the optimal thruster configuration with desired control effectiveness over the range of selected torque commands. An optimization technique called Particle Swarm Optimization is used for the numerical experiments. The validity of the solution is checked through computer simulations.