• 대한전기학회논문지
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• 제34권6호
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• pp.230-237
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• 1985

Shortest path calculations for a large-scale network have to be performed using a decomposition techniqre, since the calculations require large memory size which increases by the square of the number of vertices in the network. Also, the calculation time increases by the cube of the number of vertices in the network. In the decomposition technique,the network is broken into a number of smaller size subnetworks for each of which shortest paths are computed. A union of the solutions provides the solution of the original network. In all of the decomposition algirithms developed up to now, boundary vertices which divide all the subnetworks have to be included in computing shortest paths for each subnetwork. In this paper, an improved algorithm is developed to reduce the number of boundary vertices to be engaged. In the algorithm, only those boundary vertices that are directly connected to the subnetwork are engaged. The algorithm is suitable for an application to real time computation using a parallel processor system which consists of a number of micro-computers or prcessors. The algorithm has been applied to a 39- vertex network and a 232-vertex network. The results show that it is efficient and has better performance than any other algorithms. A parallel processor system has been built employing an MZ-80 micro-computer and two Z-80 microprocessor kits. The former is used as a master processor and the latter as slave processors. The algorithm is embedded into the system and proven effective for real-time shortest path computations.

• Journal of Power Electronics
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• 제10권2호
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• pp.132-137
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• 2010

Interleaving techniques are widely used to reduce input/output ripples and to increase the power capacity of boost converters operating in critical conduction mode. Two types of phase-shift control schemes are studied in this paper, the turn-on time shifting method and the turn-off time shifting method. It is found that although the turn-off time shifting method exhibits better performance, it suffers from sub-harmonic oscillations at high input voltages. To solve this problem, an intensive quantitative analysis of the sub-harmonic oscillation phenomenon is made in this paper. Based upon that, a novel modified turn off time shifting control scheme for interleaved boost converters operating in critical conduction mode is proposed. An important advantage of this scheme is that both the master phase and the slave phase can operate stably in critical conduction mode without any oscillations in the full input voltage range. This method is implemented with a FPGA based digital PWM control platform, and tests were carried out on a two-phase interleaved boost PFC converter prototype. Experimental results demonstrated the feasibility and performance of the proposed phase-shift control scheme.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2005년도 추계학술대회 논문집
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• pp.163-168
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• 2005

LORAN-C 는 유일하게 남아있는 지상파 항법시스템으로서 현재 전세계적인 체인을 형성하고 있으며, 우리나라에서는 GRI 9930의 코리아 체인(주국 : 포항, 종국 : 광주, 게사시, 니지마, 우스리스크)을 운영하고 있다. 그러나 LORAN-C는 사용자의 감소 및 시설의 노후화로 인하여 현재 미국에서는 새로운 시스템으로의 개선을 모색하고 있는 중이다. 이와 관련하여 국제적인 추세와 정책방향을 분석하고 기술개발 상황을 파악하여 우리나라의 LORAN-C에 대한 정책방향을 수립하는 것이 현재 절실히 필요한 시점이다. 본 연구에서는 우리나라 LORAN-C 현황 및 국제적인 동향 및 기술개발 상황을 파악하여 우리나라의 향후 LORAN-C에 대한 정책수립 방향을 제안한다.

• 대한의용생체공학회:의공학회지
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• 제29권3호
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• pp.179-186
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• 2008

This paper presents a portable tele-assessment system designed for remote evaluation of the hypertonic elbow joint of neurologically impaired patients. A patient's upper limb was securely strapped to a portable limb-stretching device which is connected through Internet to a portable haptic device by which a clinician remotely moved the patient's elbow joint and felt the resistance from the patient. Elbow flexion angle and joint torques were measured from both master and slave devices and bilaterally fed back to their counterparts. In order to overcome problems associated with the network latency, two different tele-operation schemes were proposed depending on relative speed of tasks compared to the amount of time delay. For slow movement tasks, the bilateral tele-operation was achieved in real-time by designing control architectures after causality analysis. For fast movement tasks, we used a semi-real-time tele-operation scheme which provided the clinicians with stable and transparent feeling. The tele-assessment system was verified experimentally on patients with stroke. The devices were made portable and low cost, which makes it potentially more accessible to patients in remote areas.

• 한국산학기술학회논문지
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• 제7권6호
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• pp.1122-1128
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• 2006

본 연구에서는 가스 체적 데이터를 체크하기 위하여 마이크로콘트롤러 ATmega128를 사용한 무선 데이터로거 시스템을 제작하였다. 본 시스템에서 마스터와 슬레이브 사이에 RF 무선통신을 사용하였고, 서버와 클라이언트간의 통신은 TCP/IP 프로토콜의 네트워크 환경에서 소켓통신으로 동작하도록 하였으며, 모니터링 프로그램은 Visual C++으로 GUI 환경에 적합한 소프트웨어로 제작하였다. 이 시스템은 소형, 저가격으로 쉽게 구현할 수 있으며, 마이크로콘트롤러 실험의 프로젝트 과제로 유용하게 사용될 수 있을 것이다.

• Journal of Communications and Networks
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• 제4권3호
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• pp.161-169
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• 2002

Ad hoc wireless networks involving large populations of scattered communication nodes will play a key role in the development of low power, high capacity, interactive, multimedia communication networks. Such networks must support arbitrary network connections and provide coverage anywhere and anytime. This paper partitions such arbitrarily connected network architectures into three distinct groups, identifies the associated dual network architectures and counts the number of network architectures assuming there exist N network nodes. Connectivity between network nodes is characterized as a random event. Defining the link availability P as the probability that two arbitrary network nodes in an ad hoc network are directly connected, the network connection probability $ \integral_n$(p) that any two network nodes will be directly or indirectly connected is derived. The network connection probability $ \integral_n$(p) is evaluated and graphically demonstrated as a function of p and N. It is shown that ad hoc wireless networks containing a large number of network nodes possesses the same network connectivity performance as does a fixed network, i.e., for p>0, $lim_{N\to\infty} Integral_n(p)$ = 1. Furthermore, by cooperating with fixed networks, the ad hoc network connection probability is used to derive the global network connection probability for hybrid networks. These probabilities serve to characterize network connectivity performance for users of wireless ad hoc and hybrid networks, e.g., IEEE 802.11, IEEE 802.15, IEEE 1394-95, ETSI BRAN HIPERLAN, Bluetooth, wireless ATM and the world wide web (WWW).

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 학술회의 논문집 정보 및 제어부문 B
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• pp.563-566
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• 2003

We have designed the power control unit which belongs to the power cabinet and controls the power supplied to Control Rod Drive Mechanism(CRDM) as a digital system based on Digital Signal Processor(DSP). The power control unit dualized as the form of Master/Slave has had its increased reality. The Central Process Unit(CPU) board of a power control unit possesses two Digital Signal Processors(DSPs) of the control DSP for performing the tasks of power control and system monitoring and the communication of the Control DSP and the Communication DSP. To accomplish the functions requested in the power control unit effectively, we have installed Field Programmable Gate Arrays(FPGAS) on the CPU board and have FPGAs perform the memory mapping, the generation of each chip selection signal, the giving and receiving of the signals between the power controllers dualized, the fault detection and the generation of the firing signals.

• 한국소음진동공학회논문집
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• 제22권10호
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• pp.949-958
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• 2012

Position tracking control of a link of a slave manipulator which needed to track the corresponding link of a master manipulator was addressed in this paper. Since driving torque from motor is transmitted through a set of flexible cable to link, the motion control system is modeled by a two-mass model connected with elastic coupling which has finite stiffness. Relative vibration of two-mass resonant system is a serious problem to operate manipulator. This paper proposed sliding mode control to reduce resonant vibration and fine position tracking control. Also, a pseudo-sliding mode control which uses a saturation function instead of a signum function was discussed and showed that the pseudo-sliding mode control can improve disturbance regulation performance as well as guarantees fine command tracking without chattering which is an inherent drawback of basic sliding mode control. In addition, a disturbance observer based sliding mode control has been suggested to improve disturbance regulation performance. The feasibility of the proposed control design was verified along with some simulation results.

• 한국산학기술학회논문지
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• 제12권11호
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• pp.5110-5116
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• 2011

본 논문에서는 산업용 필드 버스 프로토콜 중 신호적으로 가장 안정하다고 알려져 있는 CAN(Controller Area Network) 프로토콜을 이용하여 자동차용 전동 거울의 멀티플렉싱 제어 시스템을 제안하고자 한다. 이를 위하여 하나의 마스터 컨트롤러와 입/출력을 각각 담당하는 2개의 슬레이브 컨트롤러를 설계하여 구현하고(H/W), 이러한 각 서브 시스템 들의 효과적인 동작과 통신을 위한 Application Layer를 구현(S/W)하였다. 구현된 전체 시스템은 실제 자동차용 전동 거울에 장착하여 실험함으로써 최소한의 전장 요소들만으로 효과적인 시스템의 운용 및 제어가 가능함을 보이고자 한다.

• 로봇학회논문지
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• 제14권1호
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• pp.50-57
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• 2019

This work presents a design and control method for a flexible robot arm operated by a wire drive that follows human gestures. When moving the robot arm to a desired position, the necessary wire moving length is calculated and the motors are rotated accordingly to the length. A robotic arm is composed of a total of two module-formed mechanism similar to real human motion. Two wires are used as a closed loop in one module, and universal joints are attached to each disk to create up, down, left, and right movements. In order to control the motor, the anti-windup PID was applied to limit the sudden change usually caused by accumulated error in the integral control term. In addition, master/slave communication protocol and operation program for linking 6 motors to MYO sensor and IMU sensor output were developed at the same time. This makes it possible to receive the image information of the camera attached to the robot arm and simultaneously send the control command to the robot at high speed.