• 대한전기학회논문지
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• 제43권4호
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• pp.543-552
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• 1994

This paper presents a decentralized quadratic regulation architecture with feedforward neural networks for the control problem of complex systems. In this method, the decentralized technique was used to treat several simple subsystems instead of a full complex system in order to reduce training time of neural networks, and the neural networks' nonlinear mapping ability is exploited to handle the nonlinear interaction variables between subsystems. The decentralized regulating architecture is composed of local neuro-controllers, local neuro-identifiers and an overall interaction neuro-identifier. With the interaction neuro-identifier that catches interaction characteristics, a local neuro-identifier is trained to simulate a subsystem dynamics. A local neuro-controller is trained to learn how to control the subsystem by using generalized Backprogation Through Time(BTT) algorithm. The proposed neural network based decentralized regulating scheme is applied in the power System Stabilization(PSS) control problem for an imterconnected power system, and compared with that by a conventional centralized LQ regulator for the power system.

• 한국정보전자통신기술학회논문지
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• 제17권1호
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• pp.47-52
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• 2024

코로나 펜데믹을 거치면서 중앙정부, 지방정부, 민간사업자를 중심으로 블록체인 기반 탈중앙화 신원인증(Decentralized ID) 기술 활용 및 고도화 연구가 다양한 분야에서 활발하게 진행되고 있다. 본 논문에서는 기존 중앙 서버 기반 신원인증을 탈중앙화 기반으로 변경하기 위해 하이퍼레저 패브릭 기반으로 개발한 결과를 소개한다. 이러한 개발 결과는 상용화 목적의 신원인증 시스템에 보안성, 투명성을 강화하여 사용자 ID 발급, 조회, 폐기에 대해 안정적인 서비스를 제공할 수 있다. 또한, 탈중앙화된 신원인증 시스템은 DID 생성 262,000 rps, DID 조회 1,850 rps 성능과 DID VP 생성 200 rps, DID VP 조회 220 rps 이하의 성능 결과를 공인 인증을 통해 검증하였다.

• 한국산학기술학회논문지
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• 제21권7호
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• pp.156-161
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• 2020

복수 무인기를 운영하는 환경에서 분산 임무 할당 알고리즘의 사용은 임무를 지휘 통제하는 중앙 관제 시스템이 없기 때문에 중앙 집중식 임무 할당 방식에 비해 무인기의 임무 중 탈락 이벤트로부터 보다 큰 강건성을 가지게 된다. 또한 무인기 스스로 상황을 인지하고 통신을 통해 임무를 재할당 하는 방식이기 때문에 임무 반경 또한 더욱 넓힐 수 있는 장점을 가지고 있다. 하드웨어 성능이 향상되고 비용이 감소함에 따라 임무 환경에서의 복수 무인기 운용에 대한 필요성이 증대되고 있으며, 작전 반경이 넓고 단일 고장에 강건한 분산 임무 할당 알고리즘에 대한 연구 필요성이 대두되고 있다. 본 논문은 대표적인 분산 임무할당 알고리즘인 CBBA를 기반으로 하여, 기존에 점 좌표로 단순화 되어 설정된 임무 종류를 점 좌표에 대한 감시 업무와 선형 경로의 정찰 임무로 구분하여 보다 현실에서의 임무 상황을 반영할 수 있도록 발전시켰다. 본 연구의 결과로서 복수무인기가 과다 임무가 부여된 상황에서 동일한 임무위치 및 보상을 갖는 상황을 몬테 카를로 시뮬레이션을 통해 최종 보상합(global reward)을 비교한다.

• 한국항공우주학회지
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• 제49권12호
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• pp.981-988
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• 2021

본 논문에서는 다수 고정익 소형무인기 군집비행을 위한 분산형 유도 알고리듬 설계를 다룬다. 군집비행을 통한 임무 수행을 위해서 각 무인기들은 집결, 선회, 경로점, 개별 비행 등의 기동이 필요하다. 이를 위해서는 경로 추종, 떼비행, 충돌 회피가 요구된다. 본 논문에서는 상기 기동들을 수행하기 위해 벡터필드(경로 추종), 증강 쿠커-스메일 모델(떼비행), 포텐셜 필드(충돌 회피) 기법들을 활용한 통합 유도 알고리듬을 제안한다. 통합 유도 명령 생성을 위해 각 기법에서 생성된 유도 명령을 가중치에 따라 혼합할 수 있게 설계하며, 19대의 소형 고정익 무인기를 이용한 비행시험을 통해 제안한 군집 유도 알고리듬의 성능을 확인하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1909-1914
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• 2004

Passive velocity field control (PVFC) was previously developed for fully mechanical systems, in which the motion task was specified behaviorally in terms of a velocity field, and the closed-loop was passive with respect to a supply rate given by the environment input. However the PVFC was only applied to a single manipulator, the proposed control law was derived geometrically, and the geometric and robustness properties of the closed-loop system were also analyzed. In this paper, we propose a method to apply a decentralized control algorithm to cooperative 3-wheeled mobile robots whose subsystem is under nonholonomic constraints and which convey a common rigid object in a horizontal plain. Moreover it is shown that multiple robot systems ensure stability and the velocities of augmented systems convergence to a scaled multiple of each desired velocity field for cooperative mobile robot systems.

• Journal of Electrical Engineering and Technology
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• 제10권2호
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• pp.487-495
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• 2015

This paper proposes a new robust decentralized power oscillation dampers (POD) design of doubly-fed induction generator (DFIG) wind turbine for damping of low frequency electromechanical oscillations in an interconnected power system. The POD structure is based on the practical $2^{nd}$-order lead/lag compensator with single input. Without exact mathematical model, the inverse output multiplicative perturbation is applied to represent system uncertainties such as system parameters variation, various loading conditions etc. The parameters optimization of decentralized PODs is carried out so that the stabilizing performance and robust stability margin against system uncertainties are guaranteed. The improved firefly algorithm is applied to tune the optimal POD parameters automatically. Simulation study in two-area four-machine interconnected system shows that the proposed robust POD is much superior to the conventional POD in terms of stabilizing effect and robustness.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권11호
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• pp.2561-2576
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• 2013

The ship ad-hoc network (SANET) extends the coverage of the high data-rate terrestrial communications to the ships with the reduced cost in maritime communications. Cognitive radio (CR) has the ability of sensing the radio environment and dynamically reconfiguring the operating parameters, which can make SANET utilize the spectrum efficiently. However, due to the dynamic topology nature and no central entity for data fusion in SANET, the interference brought into the primary network caused by the hidden primary user requires to be carefully managed by a sort of decentralized cooperative spectrum sensing schemes. In this paper, we propose a self-weighted decentralized cooperative spectrum sensing (SWDCSS) scheme to solve such a problem. The analytical and simulation results show that the proposed SWDCSS scheme is reliable to detect the primary user in SANET. As a result, secondary network can efficiently utilize the spectrum band of primary network with little interference to primary network. Referring the complementary receiver operating characteristic (ROC) curves, we observe that with a given false alarm probability, our proposed algorithm reduces the missing probability by 27% than the traditional embedded spectrally agile radio protocol for evacuation (ESCAPE) algorithm in the best condition.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2007년도 학술대회
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• pp.55-58
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• 2007

An adaptive subcarrier allocation scheme based on comparative superiority of opportunity cost between groups is proposed for the enhancement of system capacity and its simple implementation at the base station of a multiuser OFDM system. The proposed algorithm is similar to the blockwise or the decentralized subcarrier allocation algorithm proposed by Xiaowen et al and Alen et al, respectively. In the proposed algorithm, however, all subcarriers are grouped according to the coherence bandwidth and the comparative superiority concept, which swaps the groups between users if the system capacity is increased, is adopted for the enhancement of system capacity. In addition, the proposed algorithm provides a simple solution for the conflict problem among users by reallocating only the conflicted groups and unassigned groups instead of reallocating entire groups. Simulation results demonstrate that the proposed algorithm increases the system capacity effectively over a static, an adaptive blockwise, and a decentralized subcarrier allocation algorithms.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권2호
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• pp.595-609
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• 2020

In this study, we propose a decentralized mathematical model for predictive control of a system of multi-autonomous unmanned aerial vehicles (UAVs), also known as drones. Being decentralized and autonomous implies that all members make their own decisions and fly depending on the dynamic information received from other unmanned aircraft in the area. We consider a variety of realistic characteristics, including time delay and communication locality. For this flocking flight, we do not possess control for central data processing or control over each UAV, as each UAV runs its collision avoidance algorithm by itself. The main contribution of this work is a mathematical model for stable group flight even in adverse weather conditions (e.g., heavy wind, rain, etc.) by adding Gaussian noise. Two of our proposed variance control algorithms are presented in this work. One is based on a simple biological imitation from statistical physical modeling, which mimics animal group behavior; the other is an algorithm for cooperatively tracking an object, which aligns the velocities of neighboring agents corresponding to each other. We demonstrate the stability of the control algorithm and its applicability in autonomous multi-drone systems using numerical simulations.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.127-132
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• 2007

In this paper, to overcome local damages of structures, an uncertainty of structural model, installing sensors of structures, and economics of building system, decentralized semi-active magnetorheological(MR) damper using the displacement or velocity transferred to the response of floor installed damper is proposed. Relative magnitude between the control force of dampers and the story shear force is difined as design variables and the performance indices response spectra analysis through nonlinear time history analysis excited by seismic loads is performed according to this design variables. And the performance of this decentralized MR damper is compared with previous centralized LQR control algorithm using 3-stories benchmark building structure excited by El Centro (1940, N.S) in order to evaluate the application of building structures.