• International Journal of Aeronautical and Space Sciences
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• 제8권1호
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• pp.10-20
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• 2007

For spacecraft attitude control, reaction wheel (RW) steering laws with more than three wheels for three-axis attitude control can be derived by using a control allocation (CA) approach.1-2 The CA technique deals with a problem of distributing a given control demand to available sets of actuators.3-4 There are many references for CA with applications to aerospace systems. For spacecraft, the control torque command for three body-fixed reference frames can be constructed by a combination of multiple wheels, usually four-wheel pyramid sets. Multi-wheel configurations can be exploited to satisfy a body-axis control torque requirement while satisfying objectives such as minimum control energy.1-2 In general, the reaction wheel steering laws determine required torque command for each wheel in the form of matrix pseudo-inverse. In general, the attitude control command is generated in the form of a feedback control. The spacecraft body angular rate measured by gyros is used to estimate angular displacement also.⁵ Combination of the body angular rate and attitude parameters such as quaternion and MRPs(Modified Rodrigues Parameters) is typically used in synthesizing the control command which should be produced by RWs.¹ The attitude sensor signals are usually corrupted by noise; gyros tend to contain errors such as drift and random noise. The attitude determination system can estimate such errors, and provide best true signals for feedback control.⁶ Even if the attitude determination system, for instance, sophisticated algorithm such as the EKF(Extended Kalman Filter) algorithm⁶, can eliminate the errors efficiently, it is quite probable that the control command still contains noise sources. The noise and/or other high frequency components in the control command would cause the wheel speed to change in an undesirable manner. The closed-loop system, governed by the feedback control law, is also directly affected by the noise due to imperfect sensor characteristics. The noise components in the sensor signal should be mitigated so that the control command is isolated from the noise effect. This can be done by adding a filter to the sensor output or preventing rapid change in the control command. Dynamic control allocation(DCA), recently studied by Härkegård, is to distribute the control command in the sense of dynamics⁴: the allocation is made over a certain time interval, not a fixed time instant. The dynamic behavior of the control command is taken into account in the course of distributing the control command. Not only the control command requirement, but also variation of the control command over a sampling interval is included in the performance criterion to be optimized. The result is a control command in the form of a finite difference equation over the given time interval.⁴ It results in a filter dynamics by taking the previous control command into account for the synthesis of current control command. Stability of the proposed dynamic control allocation (CA) approach was proved to ensure the control command is bounded at the steady-state. In this study, we extended the results presented in Ref. 4 by adding a two-step dynamic CA term in deriving the control allocation law. Also, the strict equality constraint, between the virtual and actual control inputs, is relaxed in order to construct control command with a smooth profile. The proposed DCA technique is applied to a spacecraft attitude control problem. The sensor noise and/or irregular signals, which are existent in most of spacecraft attitude sensors, can be handled effectively by the proposed approach.

• 정보보호학회논문지
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• 제33권5호
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• pp.721-736
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• 2023

명령 제어 프레임워크 (Command and Control Framework)는 모의 침투 및 교육용으로 개발되었으나 사이버 범죄 그룹과 같은 위협 행위자들이 악용하고 있다. 잠재적인 위협을 식별하고 선제 대응을 하는 사이버 위협 헌팅 관점에 따라 명령 제어 프레임워크가 작동하고 있는 서버를 식별하고 사전 차단하면 위험 요소 관리에 기여를 할 수 있다. 따라서, 이 논문에서는 명령 제어 프레임워크를 사전 추적할 수 있는 방법론을 제안한다. 방법론은 명령제어 프레임워크 관련 서버 목록 수집, 단계적 전달 모사, 봇넷 설정 추출, 인증서 수집 및 특징 추 출4단계로 구성된다. 또한, 상용 명령 제어 프레임워크인 코발트 스트라이크에 제안한 방법론을 적용하여 실험을 수행한다. 실험에서 수집된 비콘, 인증서에 대한 분석 내용을 공유함으로써 명령 제어 프레임워크로부터 발생할 수 있는 사이버 위협 대응 기반을 마련하고자 한다.

• 전기학회논문지
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• 제67권10호
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• pp.1395-1400
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• 2018

EO TGP(Electro-Optical Targeting Pod) is an optical tracking system which has various functions such as target tracking and image stabilization and LOS(Line of Sight) change. Especially, it is very important to move the LOS into a interest point for joystick command. When pilot move joystick in order to observe different scene, EO TGP gimbals should be operated properly. Generally, most EOTS just operate corresponding gimbal for joystick command. For example, if pilot input horizontal command in order to observe right hand screen, it just drive azimuth gimbal at any position. But in the screen, the image dosen't move in a horizontal direction because gimbal structure is Euler angle. And image rotation is occurred by elevation gimbal angle. So we need to move Pitch gimbal. So in the paper, we designed LOS moving algorithm which convert LOS command to gimbal velocity command to move LOS properly. We modeled a differential kinematic equation and then change the joystick command into velocity command of gimbals. This algorithm generate velocity command of each gimbal for same horizontal direction command. Finally, we verified performance through MATLAB/Simulink.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2016년도 전력전자학술대회 논문집
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• pp.173-174
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• 2016

This paper proposes a comparison of Voltage Oriented Control (VOC) and Direct Power Control (DPC) under command mode transition for PMSG Wind Turbines (WT). Based on a neutral point clamped three level back to back type Voltage Source Converter (VSC), proposed control scheme automatically control the generated output power to satisfy a grid requirement from the hierarchical wind farm controller. Automatic command mode transition based on the dc-link voltage error provides a command mode changing between grid command and MPPT mode. It is confirmed through PLECS simulations in Matlab. Simulation result shows that proposed control scheme of VOC and DPC achieves a much shorter transient time of generated output power than the conventional control scheme of MPPT with optimal torque control and VOC under a step response. The proposed control scheme makes it possible to provide a good dynamic performance for PMSG wind turbines in order to generate a high quality output power.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.54.2-54
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• 2001

In this paper two control strategies, command shaping control and optimal control, which aim to the reduction of the residual vibrations of the payload in a container crane system are investigated. Both control methods are open loop control. Due to unmodeled dynamics of the plant and disturbances like initial sway and wind, some residual sway always exists at the end of trolley movement. Command inputs are designed to achieve the control objectives including minimal residual vibration and robustness in the presence of unmodeled dynamics. Simulation results of various command inputs are compared in terms of arrival time, residual sway angle, robustness, and maximum sway distance during the traveling. Command shaping method provides a more competent tool than optimal control.

• 한국항공운항학회지
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• 제21권4호
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• pp.34-40
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• 2013

Attitude command response type required for enhanced handling qualities of helicopter can be implemented by mechanical automatic flight control system with SAS actuators which have limited authorities. However, the early saturation of SAS actuator hinders the helicopter from following the attitude command for large stick command. Auto-trim controller can delay SAS actuator's saturation by utilizing trim actuators and allows the attitude command response type for larger stick command. This paper describes the control law for limited authority system of helicopter with auto-trim. Limited authority system is applied to BO-105 linear dynamic model and simulation is performed along with handling quality analysis.

• 제어로봇시스템학회논문지
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• 제10권9호
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• pp.847-854
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• 2004

In this paper, It is studied to control and to monitor the remote system state using HTTP(Hyper Text Transfer Protocol) object communication. The remote control system is controlled by using a web browser or a application program. This system is organized by three different part depending on functionality-server part, client part, controller part. The java technology is used to composite the server part and the client part and C language is used for a controller. The server part is waiting for the request of client part and then the request is reached, the server part saves client data to the database and send a command set to the client part. The administrator can control the remote system just using a web browser. Remote part is worked by timer that is activated per 1 second. It gets the measurement data of the controller part, and then send the request to the server part and get a command set in the command repository of server part using the client ID. After interpreting the command set, the client part transfers the command set to the controller part. Controller part can be activated by the client part. If send command is transmitted by the client part, it sends sensor monitoring data to the client part and command set is transmitted then setting up the value of the controlled system.

• 제어로봇시스템학회논문지
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• 제14권1호
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• pp.88-94
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• 2008

In this paper, a design method of a missile guidance command is presented considering the dynamics of missile control systems. The design of a new guidance command is based on the well-known PNG(propotional navigation guidance) laws. The missile control system dynamics cause the time-delays of the PN guidance command and degrade the performance of original guidance laws which are designed under the assumption of the ideal missile control systems. Using a backstepping method, these time-delay effects can be compensated. In order to implement the guidance command developed by the backstepping procedure, it is required to measure or calculate the successive time-derivatives of the original guidance command, PNG and other kinematic variables such as the relative distance. Instead of directly using the measurements of these variables and their successive derivatives, a simple disturbance observer technique is employed to estimate a guidance command described by them. Using Lyapunov method, the performance of a newly developed guidance command is analyzed against a target maneuvering with a bounded and time-varying acceleration.

• 한국시뮬레이션학회논문지
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• 제20권4호
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• pp.167-175
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• 2011

미래전이 네트워크중심전(NCW, Network Centric Warfare)으로 변화함에 따라 세계적으로 지휘통제의 효과도에 관한 관심이 점증하고 있다. 과거의 기동과 타격자산 중심의 소모전 위주의 전투와 달리, 현대전은 정보의 획득과 유통이 중요시되는 정보 네트워크 기반의 전쟁으로서 C4ISR(Command, Control, Communications, Computers, Intelligence, Surveillance and Reconnaissance) 체계가 핵심적인 역할을 담당할 것이라는 데는 재론의 여지가 없다. 그럼에도 불구하고 지휘통제가 전투에 기여하는 효과의 정도를 측정하는 방법론이나 효과 반영체계 등을 명확하게 설명할 방법을 갖추고 있지 못한 실정이다. 본 연구에서는 네트워크중심작전의 기반이 되는 C4ISR 체계에 의한 효과도 증진을 개념적으로 설명할 수 있는 프레임워크인 미국방부가 개발한 NCO-CF(Network Centric Operations-Conceptual Framework)에 대하여 살펴보았다. 그리고 NCO-CF를 기반으로 하여 지휘통제 효과도 모의분석을 위한 평가기준을 도출하기 위한 방법론을 제시하였다. 사례연구로 합동작전의 지휘통제 체계에 이 방법론을 적용하여 모의분석을 위한 평가기준을 도출하였다.

• 한국군사과학기술학회지
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• 제14권4호
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• pp.556-563
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• 2011

Recently, the development of military system is focused on Network Centric Warfare. But, there is no deployed Command and Control System for Missile System in the country. Therefore, Command and Control System for Missile System was simulated to predict feasibility for the future development in this paper. The contents of the design and implementation for simulated system are described in details. Besides, a method for avoiding collisions in 1:N radio communication environment is proposed as the future work. The simulated system in this paper will be a help to developing Command and Control System for Missile System in the future.