• 한국정보과학회논문지:정보통신
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• 제30권2호
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• pp.260-269
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• 2003

기존의 분산 객체 미들웨어가 제공하는 RPC(Remote Procedure Call) 기반의 메시지전송 방식은 내부 오버헤드로 인해 실시간성을 요구하는 스트림 데이타의 전송에는 부적합하다. 그래서 OMG (Object Management Group)에서는 분산 환경에서도 실시간 스트리밍을 지원 할 수 있는 새로운 AV (Audio and Video) 스트림 서비스 참조 모델을 제안하였다. 그러나 이 모델은 오직 참조 모델이기 때문에 실제 구현 방법에 따라 재 정의해야 할 부분이 많이 남아 있다. 특히 실제 네트워크 환경을 고려한 혼잡 제어와 같은 기능이 없기 때문에 스트림 전송의 QoS를 제어할 수가 없다. 이러한 고려는 최근 연구되어 지고 있는 다양한 스트림 전송 플랫폼들이 가져야 할 고급 기능으로 전체 네트워크의 효율 증가를 위해서도 반드시 필요하다. 본 논문에서는 분산 환경의 장점을 최대한 부각시킬 수 있는 OMG의 스트림 서비스 참조 모델을 재 정의한 스트림 전송 플랫폼을 설계하고 구현하였다. 제안한 플랫폼은 스트림 전송을 위한 새로운 TCP-Friendly 프로토콜인 SRTP(Smart RTP)를 하부 구성 요소로 제공하며 이를 이용하여 본 플랫폼을 통한 스트리밍 응용들의 효율을 향상시켰다.

• 한국통신학회논문지
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• 제23권8호
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• pp.2064-2071
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• 1998

휴대용 기기에서 자체 발진하여 클럭원으로 사용되는 TCXO의 출력과 같은 작은 진폭(400mV)의 정현파 입력을 내부 논리회로의 클럭원으로 사용하기 위한 파형정형 및 50%의 듀티 비(duty ratio)의 출력을 가지는 새로운 디지털 클럭레벨 변환기를 설계, 개발 하였다. 정, 부 두 개의 비교기, RS 래치, 차아지 펌프, 기준 전압 발생기로 구성된 새로운 신호 변환회로는 출력파형의 펄스 폭을 감지하고, 이 결과를 궤환루프로 구성하여 입력 비교기 기준 전압단자로 궤환시킴으로서 다지털 신호레벨의 정확한 50%의 듀티 비를 가진 출력을 생성할 수 있다. 개발한 레벨변환기는 ADC등의 샘플링 클럭원, PLL 또는 신호 합성기의 클럭원으로 사용할 수가 있다. 설계는 $0.8\mu\textrm{m}$ double metal double poly analog CMOS 공정을 사용하고, BSIM3 model을 사용하였으며, 실험결과 370mV의 정현파 입력율 50 + 3%의 듀티 비를 가진 안정된 논리레벨 출력 동작특성을 얻을 수 있었다.

• 전기학회논문지
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• 제58권1호
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• pp.203-209
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• 2009

The purpose of this study is to develop a minimally constraint joint angle measurement system for the feedback control of FES (functional electrical stimulation) locomotion. Feedback control is desirable for the efficient FES locomotion, however, the simple on-off control schemes are mainly used in clinic because the currently available angle measurement systems are heavily constraint or cosmetically poor. We designed a new angle measurement system consisting of a magnet and magnetic sensors located below and above the ankle joint, respectively, in the rear side of ipsilateral leg. Two magnetic sensors are arranged so that the sensing axes are perpendicular each other. Multiple positions of sensors attachment on the shank part of the ankle joint model and also human ankle joint were selected and the accuracy of the measured angle at each position was investigated. The reference ankle joint angle was measured by potentiometer and motion capture system. The ankle joint angle was determined from the fitting curve of the reference angle and magnetic flux density relationship. The errors of the measured angle were calculated at each sensor position for the ankle range of motion (ROM) $-20{\sim}15$ degrees (dorsiflexion as positive) which covers the ankle ROM of both stroke patients and normal subjects during locomotion. The error was the smallest with the sensor at the position 1 which was the nearest position to the ankle joint. In case of human experiment, the RMS (root mean square) errors were $0.51{\pm}1.78(0.31{\sim}0.64)$ degrees and the maximum errors were $1.19{\pm}0.46(0.68{\sim}1.58)$ degrees. The proposed system is less constraint and cosmetically better than the existing angle measurement system because the wires are not needed.

• Korean Journal of Geomatics
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• 제5권1호
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• pp.7-19
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• 2005

Photogrammetric mapping procedures have gone through major developments due to significant improvements in its underlying technologies. The availability of GPS/INS systems greatly assist in direct geo-referencing of the acquired imagery. Still, photogrammetric datasets taken without the aid of positioning and navigation systems need control information for the purpose of surface reconstruction. Point features were, and still are, the primary source of control for the photogrammetric triangulation although other higher-order features are available and can be used. LIDAR systems supply dense geometric surface information in the form of three dimensional coordinates with respect to certain reference system. Considering the accuracy improvement of LIDAR systems in the recent years, LIDAR data is considered a viable supply of photogrammetric control. To exploit LIDAR data, new challenges are poised concerning the representation and reference system by which both the photogrammetric and LIDAR datasets are described. In this paper, registration methodologies will be devised for the purpose of integrating the LIDAR data into the photogrammetric triangulation. Such registration methodologies have to deal with three issues: registration primitives, transformation parameters, and similarity measures. Two methodologies will be introduced that utilize straight-line and areal features derived from both datasets as the registration primitives. The first methodology directly incorporates the LIDAR lines as control information in the photogrammetric triangulation, while in the second methodology, LIDAR patches are used to produce and align the photogrammetric model. Also, camera self-calibration experiments were conducted on simulated and real data to test the feasibility of using LIDAR patches for this purpose.

• Journal of Power Electronics
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• 제15권5호
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• pp.1244-1255
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• 2015

This paper presents a new multi-machine robust control based on an electric differential system for electric vehicle (EV) applications which is composed of four in-wheel permanent magnet synchronous motors. It is based on a new master-slave direct torque control (DTC) algorithm, which is used for the control of bi-machine traction systems based on a speed model reference adaptive system observer. The use of an electric differential in the design of a new EV constitutes a technological breakthrough. A classical system with a multi-inverter and a multi-machine comprises a three-phase inverter for each machine to be controlled. Another approach consists of only one three-phase inverter for several permanent magnet synchronous machines. The control of multi-machine single-inverter systems is the subject of this study. Several methods have been proposed for the control of multi-machine single-inverter systems. In this study, a new master-slave based DTC strategy is developed to generate an electric differential system. The entire system is simulated by Matlab/Simulink. The simulation results show the effectiveness of the new multi-machine robust control based on an electric differential system for use in EV applications.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.720-723
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• 2005

Ship motion is a complex controlled process with several hydrodynamic parameters that vary in wide ranges with respect to ship load condition, speed and surrounding conditions (such as wind, current, tide, etc.). Therefore, to effectively control ships in a designed track is always an important task for ship masters. This paper presents an effective adaptive autopilot ships that ensure the optimal accuracy, economy and stability characteristics. The PID control methodology is modified and parameters of a PID controller is designed to satisfy conditions for an optimal objective function that comprised by heading error, resistance and drift during changing course, and loss of surge velocity or fuel consumption. Designing of the controller for course changing process is based on the Model Reference Adaptive System (MRAS) control theory, while as designing of the automatic course keeping process is based on the Self Tuning Regulator (STR) control theory. Simulation (using MATLAB software) in various disturbance conditions shows that in comparison with conventional PID autopilots, the designed autopilot has several notable advantages: higher course turning speed, lower swing of ship bow even in strong waves and winds, high accuracy of course keeping, shorter time of rudder actions smaller times of changing rudder direction.

• 대한전기학회논문지:시스템및제어부문D
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• 제51권5호
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• pp.182-189
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• 2002

This paper presents a framework of hybrid dynamic control systems for the motion control of wheeled mobile robot systems with nonholonomic constraints. The hybrid control system has the 3-layered hierarchical structure: digital automata for the higher process, mobile robot system for the lower process, and the interface as the interaction process between the continuous dynamics and the discrete dynamics. In the hybrid control architecture of mobile robot, the continuous dynamics of mobile robots are modeled by the switched systems. The abstract model and digital automata for the motion control are developed. In high level, the discrete states are defined by using the sensor-based search windows and the reference motions of a mobile robot in low level are specified in the abstracted motions. The mobile robots can perform both the motion planning and autonomous maneuvering with obstacle avoidance in indoor navigation problem. Simulation and experimental results show that hybrid system approach is an effective method for the autonomous maneuvering in indoor environments

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.659-664
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• 2000

Fuel-consumption and catalyst-out emissions of a parallel hybrid electric vehicle are affected by operating region of an engine. In many researches, It is generally known that it is profitable in fuel- consumption to operate engine in OOL(Optimal Operating Line). We established the mathematical model of a parallel hybrid electric vehicle, which is linear time-invariant. To operate an engine in OOL, we applied RHC(Receding Horizon Control) to the driving control of a parallel hybrid electric vehicle. And it is known that the RHC has advantages such as good tracking performance under state and control constraints. This RHC is obtained by using linear matrix inequality (LMI) optimization. In this paper, there are three main topics. First, without state and control constraints, the optimal tracking of OOL was simulated. Second, with state and control constraints by engine and motor performances, the optimal tracking of OOL was simulated. In the last, we studied on the optimal gear ratio. That is to say, we combined the RHC and the iterative simulation to extract the optimal gear ratio. In this simulation, the vehicle is commanded to track the reference vehicle trajectory and the engine is operated in the optimal operating region which is made by the state constraints.

• 대한전기학회논문지
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• 제37권3호
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• pp.171-179
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• 1988

본 논문은 MRAC방식을 이용하여 비행체 조종장치의 제어기 설께에 관하여 다루었다. 적응제어 시스템의 구성은 NARENDRA와 VALAVANI가 제안한 구조를 토대로 하여 프랜트의 상대차수가 $n^{*}=2$인 경우에 대하여 고찰하였다. 비행체 조종장치는 단일 입.출력을 갖는 제어시스템으로 근사화하였고, 제어입력은 기준모델과 프랜트의 입.출력관계로부터 얻는다. 설계된 제어시스템의 타당성을 검토하기 위하여 프랜트가 애널로그 모델인 경우롸 비행자세를 나타내줄 수 있는 비행운동테이블을 포함하는 각각의 경우에 대하여 시뮬레이션하였고, 그 결과 검토하였다.

• 대한전기학회논문지:시스템및제어부문D
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• 제49권3호
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• pp.117-123
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• 2000

A new control method for precision robust position control of a PMSM (Permanent Magnet Synchronous Motor) using asymptotically stable adaptive load torque observer is presented in the paper. Precision position control is obtained for the PMSM system approximately linearized using the field-orientation method. Recently, many of these drive systems use the PMSM to avoid backlashes. However, the disadvantages of the motor are high cost and complex control because of nonlinear characteristics. Also, the load torque disturbance directly affects the motor shaft. The application of the load torque observer is published in [1] using fixed gain. However, the motor flux linkage is not exactly known for a load torque observer. There is the problem of uncertainty to obtain very high precision position control. Therefore, a model reference adaptive observer is considered to overcome the problem of unknown parameter and torque disturbance in this paper. The system stability analysis is carried out using Lyapunov stability theorem. As a result, asymptotically stable observer gain can be obtained without affecting the overall system response. The load disturbance detected by the asymptotically stable adaptive observer is compensated by feedforwarding the equivalent current which gives fast response. The experimental results are presented in the paper using DSP TMS320c31.