• 한국항공우주학회지
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• 제41권3호
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• pp.217-225
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• 2013

통상적인 쿼드로터 항공기는 네 개 로터의 회전 속도에 의한 추력 벡터의 크기를 조절하여 자세를 제어한다. 본 연구에서는 기존에 개발된 쿼드로터 항공기의 단점을 개선하기 위해서 사이클릭 피치 제어가 가능한 쿼드로터 항공기를 설계하였다. 콜렉티브와 사이클릭 제어를 사용하는 쿼드로터 항공기는 각 로터의 회전속도를 모두 동일하게 유지함으로써 진동에 의한 구조적인 문제를 해소할 수 있으며, 12개의 자유도를 가지므로 다양한 자세에서의 비행이 가능하기 때문에 자동 비행과 실용적 임무가 가능한 고성능 항공기로서 적합하다. 본 연구에서 개발하는 쿼드로터 항공기의 모델링은 FLIGHTLAB을 이용하여 비선형 모델을 구성하였으며, 각 비행 조건에서의 선형 모델을 이용하여 LQR 제어기 설계 및 비선형 시뮬레이션을 통해 제어기의 성능을 검증하였다. 본 논문은 사이클릭 피치 제어가 가능한 쿼드로터의 모델링 및 시뮬레이션 결과를 보여준다.

• International Journal of Concrete Structures and Materials
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• 제7권3호
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• pp.225-238
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• 2013

In this study, a two-layer feed-forward neural network was constructed and applied to determine a mapping associating mix design and testing factors of cement-nano silica (NS)-rice husk ash ternary blended concrete samples with their performance in conductance to the water absorption properties. To generate data for the neural network model (NNM), a total of 174 field cores from 58 different mixes at three ages were tested in the laboratory for each of percentage, velocity and coefficient of water absorption and mix volumetric properties. The significant factors (six items) that affect the permeability properties of ternary blended concrete were identified by experimental studies which were: (1) percentage of cement; (2) content of rice husk ash; (3) percentage of 15 nm of $SiO_2$ particles; (4) content of NS particles with average size of 80 nm; (5) effect of curing medium and (6) curing time. The mentioned significant factors were then used to define the domain of a neural network which was trained based on the Levenberg-Marquardt back propagation algorithm using Matlab software. Excellent agreement was observed between simulation and laboratory data. It is believed that the novel developed NNM with three outputs will be a useful tool in the study of the permeability properties of ternary blended concrete and its maintenance.

• 전기학회논문지
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• 제62권7호
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• pp.943-949
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• 2013

Recently, an electric vehicle (EV) has been become a huge issue in the automotive industry. The EV has many electrical units: electric motors, batteries, converters, etc. The DC distribution power system (DPS) is essential for the EV. The DC DPS offers many advantages. However, multiple loads in the DC DPS may affect the severe instability on the DC bus voltage. Therefore, a voltage bus conditioner (VBC) may use the DC DPS. The VBC is used to mitigate the voltage transient on the bus. Thus, a suitable control technique should be selected for the VBC. In this research, Current controller with fixed switching frequency is designed and applied for the VBC. The DC DPS consist of both a resistor load and a boost converter load. The load variations cause the instability of the DC DPS. This instability is mitigated by the VBC. The simulation results by Matlab simulink and experimental results are presented for validating the proposed VBC and designed control technique.

• 전기학회논문지
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• 제66권9호
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• pp.1309-1316
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• 2017

As penetration level of Distributed Generations (DGs) on weak distribution networks gets higher, voltage rise problem can often occur due to reverse power which is not expected in conventional distribution networks. It, however, cannot be effectively solved by using conventional voltage regulating devices such as On-Load Tap Changers (OLTCs), Step Voltage Regulators (SVRs) because those do not consider the presence of DGs when determining relevant setting parameter for voltage regulation. This paper presents a scheme for voltage regulation using coordinated control between OLTC and DGs which can actively participate in the regulation. The scheme decides which device should be operated first based on the characteristics of regulating devices, in order to prevent unnecessary operation of output changes of DG and excessive tap changing operation of OLTC. Computer simulations considering daily irradiation of PV and load curve are performed by using MATLAB Simulink and performance comparison between the presented scheme and conventional ones is also made. It can be concluded from simulation results that the scheme presented is very effective to regulate voltages in distribution networks with multiple DGs.

• Journal of information and communication convergence engineering
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• 제8권1호
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• pp.1-5
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• 2010

In this paper, we propose for improving QoS in wireless micro cellular network using Cellular-IP/PRC(Paging Route Cache) with Paging Cache and Route Cache in Cellular-IP and propose for performance of realtime and non-real time handoff service using Handoff state machine Paging Route Cache. Although the Cellular-IP/PRC technology is devised for mobile internet communication, it bas its vulnerability in frequent handoff environment. On the other hand, Cellular IP combines the capability of cellular networks to provide high performance handoff and efficient location management of active and idle mobile users with the inherent flexibility, robustness and scalability found in IP networks. Also Cellular-IP/PRC use semi-soft handoff. During semi-soft hand off a mobile host may be in contact with either of the old and new base stations and receive packets from them. Packets intended to the mobile node are sent to both base stations and buffered, so when the mobile host eventually moves to the new location it can continue to receive packets without interruption. It should be suitable for realtime service such as multimedia traffic. But, much waste of resource will occur in this method, especially for non-real time services such as FTP and E-mail. Therefore, a new algorithm that performs different handoff according to characteristic of each traffic by use of reserved field in IP packet is proposed in this thesis. This hand off state machine using differentiated handoff improves quality of services in Cellular-IP/PRC. Suggested algorithm shows better performance than existing technology in wireless mobile internet communication environment. Matlab simulation results are improving QoS, show call drop and call blocking provided to Paging Router Cache during handoff state machine in Cellular-IP/PRC.

• 전력전자학회논문지
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• 제6권6호
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• pp.514-524
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• 2001

종전의 평균전력이론은 3상 불평형과 같은 전원전압 조건에 따라 능동전력필터의 보상기준전류가 결정적으로 영향을 받는 문제점이 있다. 이와 같은 불평형된 능동전력 필터의 보상전류는 결과적으로 불평형이 되는 원인이 된다. 본 연구에서는 불평형 전원 하에서도 유효전력과 기본파 무효전력의 동기 검출법에 입각하여 비선형 부하전류의 유효성분과 기본파 무효성분 그리고 왜형 성분을 각각 독립적으로 분해가 가능한 평균전력 이론을 제시하였다. 제안된 이론은 간단한 평균전력 이론을 기반으로 하고 잇기 때문에 우선 이해사기 쉽고 구현이 간단하다는 장점이 있다. 본 연구 에서는 고속의 DSP(digital signal processor)에 의하여 이와 같은 문제을 어느정 도 해결할 수있었다. 제안된 방법의 타당성을 입증하기 위해서 TMS320C31-DSP기반의 전력분석 시스템을 제작하였다. b상 전압이 15% 불평형된 3상 3전 전원하에서 시뮬레이션 및 실험을 수행한 결과 종전의 방법에 비하여 제안된 알고리즘의 유용성을 입증할수 있었다.

• 전력전자학회논문지
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• 제18권6호
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• pp.530-539
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• 2013

In large vessels, proper water level must be maintained with a balance for right and left equilibrium by absorbing or draining sea water in ballast water tank. However, this ship's ballast-water can be drained marine organisms to local sea area by world trade and this can be a source of ecological disturb. In order to solve these problems, marine organisms must be removed in accordance with the international covenant for the emission of microorganisms. By this reason, the seawater electrolysis rectifier of low-voltage high-current rectifiers with excellent ability for microbial treatment is required. In this paper, PSFB converter will be discussed for the seawater electrolysis rectifier. Furthermore, a new output control method with the power limit operation under the limited maximum voltage condition is proposed for this rectifier. The simulation for the proposed current control method for PSFB Converter is shown using MATLAB/SIMULINK. Finally the usefulness of the proposed control method is presented by the experimental results.

• Journal of Power Electronics
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• 제18권4호
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• pp.1027-1036
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• 2018

In this paper a new generalized space vector pulse width modulation scheme is proposed based on the principle of reverse mapping to drive the switches of multilevel inverters. This projected scheme is developed based on the middle vector of the subhexagon which holds the tip of the reference vector, which plays a major role in mapping the reference vector. A new approach is offered to produce middle vector of the subhexagon which holds tip of the reference vector in the multilevel space vector plane. By using middle vector of the subhexagon, reference vector is linked towards the inner two level sub-hexagon. Then switching vectors, switching sequence and dwell times corresponding to a particular sector of a two-level inverter are determined. After that, by using the two level stage findings, the switching vectors related to exact position of the reference vector are directly generated based on principle of the reverse mapping approach and do not need to be found at n level stage. In the reverse mapping principle, the middle vector of subhexagon is added to the formerly found two level switching vectors. The proposed generalized algorithm is efficient and it can be applied to an inverter of any level. In this paper, the proposed scheme is explained for a five-level inverter and the performance is analyzed for five level and three level inverters through MATLAB. The simulation results are validated by implementing the propose scheme on a V/f controlled three-level inverter fed induction motor using dSPACE control desk.

• 전기학회논문지P
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• 제59권2호
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• pp.191-196
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• 2010

The electricity distribution system in Korea is adopting a multi-grounding system. Protection of this distribution system against lightning is performed by installing overhead ground wires over the high voltage wires, and connecting the overhead ground wires to the ground every 200 m. The ground resistance in this system is limited not to exceed $50\Omega$ and overhead ground wire and neutral wire are multiple parallel lines. Although overhead ground wire and neutral wire are installed in different locations on the same pole, this circuit configuration has duplicated functions of providing a return path for unbalanced currents and protecting the distribution system against induced lightning. Therefore, the purpose of this study is to analyze the induced lightning shielding effect according to the neutral wire installation structure of a 22.9kV distribution line in order to present a new 22.9kV distribution line structure model and characteristics. This study calculated induced lightning voltage by performing numerical analysis when an overhead ground wire is present in the multi-grounding type 22.9kV distribution line structure, and calculated the induced lightning shielding effect based on this calculated induced lightning voltage. In addition, this study proposed and analyzed an improved distribution line model allowing the use of both overhead wire and neutral wire to be installed in the current distribution lines. The result of MATLAB simulation using the conditions applied by Yokoyama showed almost no difference between the induced lightning voltage developed in the current line and that developed in the proposed line. This signifies that shielding the induced lightning voltage through overhead wire makes no difference between current and proposed distribution line structures. That is, this study found that the ground resistance of the overhead wire had an effect on the induced lightning voltage, and that the induced lightning shielding effect of overhead wire is small.

• 대한기계학회논문집A
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• 제40권2호
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• pp.229-236
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• 2016

본 연구에서는 자주박격포의 다물체동역학 모델을 만든 뒤, 포탄의 탄도학을 고려하여 시뮬레이션 하였다. 자주박격포 모델은 박격포 모델 및 차량 모델로 구성하였으며, 상용 다물체 해석 프로그램인 RecurDyn 을 사용하였다. 차량 모델은 6 자유도 강체플랫폼으로 모델링 하였으며, 박격포 발사 직후의 움직임에는 강내탄도학을 적용하였다. 강내탄도학 해석의 결과를 바탕으로, 포신을 떠난 후의 강외탄도 해석을 수행하였다. 몬테카를로 기법을 활용한 반복 해석으로 발사각과 차량 동특성에 의한 변동이 고려된 탄착점의 분산도를 구하여 사격정확도를 제시하였다.