• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1938-1943
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• 2005

Network human-robot interface is an important research topic. In home application, users access the robotic system directly via voice, gestures or through the network. Users explore a system by using the services provided by this system and to some extend users are enable to participate in a service as partners. A service may be provided by a robot, a group of robots or robots and other network connected systems (distributed sensors, information systems, etc). All these services are done in the network environment, where uncertainty such as the unstable network connection, the availability of the partners in a service, exists. Moreover, these services are controlled by several users, accessing at different time by different methods. Our research aimed at solving this problem to provide a high available level, flexible coordination system. In this paper, a multi-agent framework is proposed. This framework is validated by using our new concept of slave agents, a responsive multi-agent environment, a virtual directory facilitator (VDF), and a task allocation system using contract net protocol. Our system uses a mixed model between distributed and centralized model. It uses a centralized agent management system (AMS) to control the overall system. However, the partners and users may be distributed agents connected to the center through agent communication or centralized at the AMS container using the slave agents to represent the physical agents. The system is able to determine the task allocation for a group of robot working as a team to provide a service. A number of experiments have been conducted successfully in our lab environment using Issac robot, a PDA for user agent and a wireless network system, operated under our multi agent framework control. The experiments show that this framework works well and provides some advantages to existing systems.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.322-326
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• 1991

A real time process control package was developed in an INTEL 80386 based PC and MS OS/2 environment using MS-C and MS-FORTRAN. RTACS(Real Time Advanced Control System), process control computer software for distributed or centralized architectures, is a package which meets functional requirements specified for typical continuous process applications like chemical processes. The package consists of 5 parts, which are DB(data base), OCF(Operator Console Functions), CL (Control logic Library), MSM(Multitasking and Scheduling, Manager) and UAI(User Applications Interface), based upon a table and function block architecture to improve the system performance.

• 대한전기학회논문지
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• 제36권7호
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• pp.476-483
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• 1987

This paper analyzes centralized sampled-data control systems with feedback loops which are closed through a digital computer which generates deadbeat control law. Intermittant computer interruptions result in failure to update the desired deadbeat design procedures for the deadbeat control law under normal operation of the control computer and the assumption of any admissible computer interruption are resented. A method that guarantees asymptotic stability under all admissible computer interruptions also is presented.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권9호
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• pp.2154-2172
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• 2013

A centralized cognitive radio (CR) network is proposed and its system capacity is studied. The CR network is designed with power control and multi-user scheduling schemes to support best-effort traffics under peak interference power constraints. We provide an analytical framework to quantify its system capacity, taking into account various key factors such as interference constraints, density of primary users, cell radius, the number of CR users, and propagations effects. Furthermore, closed-form formulas are derived for its capacities when only path loss is considered in the channel model. Semi-analytical expressions for the capacities are also given when more realistic channel models that include path loss, shadowing, and small-scale fading are used. The accuracy of the proposed analytical framework is validated by Monte Carlo simulations. Illustrated with a practical example, the provided analytical framework is shown to be useful for the strategic planning of centralized CR networks.

• 전기학회논문지
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• 제64권3호
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• pp.375-383
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• 2015

The virtual power plant (VPP) is a new technology to achieve flexibility as well as controllability, like traditional centralized power plants, by integrating and operating different types of distributed energy resources (DER) with the information communication technology (ICT). Though small-sized DERs may not be controlled in a centralized manner, these are more likely to be utilized as power plants for centralized dispatch and participate in the energy trade given that these are integrated into a unified generation profile and certain technical properties such as dispatch schedules, ramp rates, voltage control, and reserves are explicitly implemented. Unfortunately, the VPP has been in a conceptual stage thus far and its common definition has not yet been established. Such a lack of obvious guidelines for VPP may lead to a further challenge of coming up with the business model and reinforcing the investment and technical support for VPP. In this context, this paper would aim to identify the definition of VPP as a critical factor in smart grid and, at the same time, discuss the details required for VPP to actively take part in the electricity market under the smart grid paradigm.

• Journal of Communications and Networks
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• 제13권4호
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• pp.327-338
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• 2011

With the incitation to reduce power consumption and the aggressive reuse of spectral resources, there is an inevitable trend towards the deployment of small-cell networks by decomposing a traditional single-tier network into a multi-tier network with very high throughput per network area. However, this cell size reduction increases the complexity of network operation and the severity of cross-tier interference. In this paper, we consider a downlink two-tier network comprising of a multiple-antenna macrocell base station and a single femtocell access point, each serving multiples users with a single antenna. In this scenario, we treat the following beamforming optimization problems: i) Total transmit power minimization problem; ii) mean-square error balancing problem; and iii) interference power minimization problem. In the presence of perfect channel state information (CSI), we formulate the optimization algorithms in a centralized manner and determine the optimal beamformers using standard convex optimization techniques. In addition, we propose semi-decentralized algorithms to overcome the drawback of centralized design by introducing the signal-to-leakage plus noise ratio criteria. Taking into account imperfect CSI for both centralized and semi-decentralized approaches, we also propose robust algorithms tailored by the worst-case design to mitigate the effect of channel uncertainty. Finally, numerical results are presented to validate our proposed algorithms.

• Journal of Electrical Engineering and Technology
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• 제11권4호
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• pp.810-819
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• 2016

Uncoordinated charging of large-scale electric vehicles (EVs) will have a negative impact on the secure and economic operation of the power system, especially at the distribution level. Given that the charging load of EVs can be controlled to some extent, research on the optimal charging control of EVs has been extensively carried out. In this paper, two possible smart charging scenarios in China are studied: centralized optimal charging operated by an aggregator and decentralized optimal charging managed by individual users. Under the assumption that the aggregators and individual users only concern the economic benefits, new load peaks will arise under time of use (TOU) pricing which is extensively employed in China. To solve this problem, a simple incentive mechanism is proposed for centralized optimal charging while a rolling-update pricing scheme is devised for decentralized optimal charging. The original optimal charging models are modified to account for the developed schemes. Simulated tests corroborate the efficacy of optimal scheduling for charging EVs in various scenarios.

• 항공우주기술
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• 제8권1호
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• pp.172-178
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• 2009

최근에 개발된 소형제트기는 조종사의 피로경감과 더불어 비행안전성 제고를 위하여 자동비행시스템이 필수적인 요소로 인식되고 있다. 또한, 소형항공기의 항공전자시스템은 집중화된 다중프로세서(centralized multi-processor)와 다중연산 계산구조(multi-process computing architectures)로서 B-777의 Integrated Modular Avionics와 유사한 시스템을 장착하는 추세이다. 이러한 소형항공기 시스템 변화는 고전적 비행방식인 조종사 중심의 비행방식에서 자동비행제어시스템(AFCS) 중심의 비행방식으로의 변화를 야기하였으며 자동 비행제어시스템의 비중은 보다 더 증가하고 있다. 이에 본 논문에서는 상용 소형항공기용 자동비행장치(Autopilot)에 대한 HILS를 구성하여 성능을 검증하였다. 또한, 현재 개발하고 있는 FBW용 FCC(Flight Control Computer)에 탑재될 자동비행 알고리듬에 대한 성능을 PILS를 통하여 확인하였고, 상용 Autopilot에 대한 HILS 결과와 같은 조건에서 비교하여 그 성능을 검증하였다.

• 한국산업정보학회논문지
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• 제16권4호
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• pp.99-105
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• 2011

본 논문은 다물체 복합시스템 인자의 변위에 강인한 중앙집중식 연속반복학습제어기(Repetitive Controller, RC)를 설계하는 방법을 소개하고자 한다. 이때 사용되는 불확실 인자들은 확률분포함수에 의해 무작위로 설정되게 된다. 분포함수를 직접 적용하는 대신, 본 제어기는 설정된 확률함수로부터 생성된 모형을 기본으로 설계하였다. 이러한 중앙집중식 복수모형 설계기법으로 엄의의 분포함수로 구성된 수많은 불확실 인자들을 다룰 수 있다. 그러므로, 제어기는 반복영역에서 수렴성을 보장하는 비용함수를 주파수영역에서 최소화함으로써 유도할 수 있다. 다물체 복합시스템에서 중앙집중식 복수모형설계 기법을 단수모형 설계기법과 함께 제안하였다.

• 정보처리학회논문지C
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• 제11C권1호
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• pp.47-54
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• 2004

컴퓨터 자원의 대용량화 및 네트워크 속도의 증가로 인하여 사용자가 네트워크를 통해 원격지의 서버에 접속하여 컴퓨터론 사용하는 요구가 증가되었다. 이에 따라 중앙집중형 컴퓨팅을 통한 응용프로그램 제공 서비스도 활성화되었다. 중앙집중형 컴퓨팅 시스템은 중앙의 대용량컴퓨터 시스템에 설치된 응용프로그램을 공유 프로토콜을 통하여 원격 사용자에게 제공하는 응용프로그램 공유 서비스(ASP： Application Service Provision) 시스템 모델이다. 중앙집중형 컴퓨팅 시스템을 통한 응용프로그램 공유 서비스는 기밀성, 가용성 무결성 등의 보안 사항이 반드시 유지되어야 한다. 기존 원격 컴퓨팅인 Telnet, FTP 접속은 단순히 파일 및 데이터의 접근 권한을 제어함으로 보안이 유지된다. 그러나 윈도우 기반 시스템의 경우 다수의 사용자가 통일한 권한을 통해 통일한 응용프로그램을 제공받기 때문에 사용자들 사이에 기밀성 및 무결성을 저해 할 수 있다. 또한 다수의 사용자가 하나의 응용프로그램에 파일열기, 복사, 서식 수정 등의 여러 기능 명령어를 전송하기 때문에 파일 및 데이터 접근 제어만을 통해서는 시스템의 기밀성 유지한 수 없다. 또한 기밀성의 문제는 곧 가용성 및 무결성의 문제로 이어질 수 있다. 본 논문에서는 윈도우 기반 중앙집중형 컴퓨팅 시스템의 응용프로그램 공유 서비스를 지원함에 있어 사용자가 실행하는 Win32 API 메시지 명령어 접근제어 시스템을 제안한다. 제안하는 시스템은 GUI(Graphical User Interface) 기반의 서버에서 사용자가 서버에 접속하여 발생하는 모든 메시지(마우스, 키보드, I/O, etc....)들을 감시한다. 감시된 메시지 기반의 명령어는 미리 설정된 사용자별 보안 정책에 기반 하여 해당 응용프로그램에게 전달 여부가 결정된다. 이러한 메시지 기반 상세 보안을 통해 기밀성 침해의 우려가 있는 메시지 명령어를 차단하고, 기능 명령어 차단에 의한 자원의 기밀성을 해결하였다.