• 제어로봇시스템학회논문지
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• 제18권2호
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• pp.156-160
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• 2012

In this paper, we investigate the effect of asynchronous haptic and video feedback on the performance of teleoperation. To analyze the effect, a tele-manipulation experiment is specially designed, which operator moves square objects from one place to another place by using master/slave telerobotic system. Task completion time and total number of falling of the object are used for evaluating the performance. Subjective study was conducted with 10 subjects in 16 different combinations of video and haptic feedback while participants didn't have any prior information about the amount of each delay. Initially we assume that synchronized haptic and video feedback would give best performance. However as a result, we found that the accuracy was increased when haptic and video feedback was synchronized, and the completion time was decreased when one of the feedback (either haptic or video) was decreased. Another interesting fact that we found in this experiment is that it showed even better accuracy when haptic information arrives little bit earlier than video information, than the case when those are synchronized.

• 천문학회보
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• 제37권2호
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• pp.184.2-184.2
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• 2012

위성의 전장품은 전기적 접속을 위해서 1:1 연결을 하는 Point-to-Point 버스 방식과 여러개의 Slave (Remote Terminal)을 갖고, 일반적으로 1개의 Master (Controller)에 의해서 연결하게 되는 버스 구조를 갖는 접속 채널을 통해서 연결이 된다. 가장 많이 사용되는 방식인 MIL-STD-1553B는 데이터 전송속도가 1Mbps이고, Transformer에 의해서 완전하게 버스와 각 전장품이 완전하게 절연이 되는 구조로, 전기적 고장이 전달되는 것을 방지할 수가 있지만, 설계의 난이도가 높다. 고속 버스는 SpaceWire를 사용하고, 100Mbps이상의 속도를 지원할 수가 있지만, LVDS등의 고속 채널 설계 및 노이즈에 민감한 특성 때문에, 저속의 통신채널에서는 사용하기 어렵다. 저속의 데이터 채널을 위해서는 UART 방식이 사용된다. UART 방식은 RS-422 방식과 RS-485 방식이 사용되지만, 1553B 또는 SpaceWire 등과 같이 프로토콜이 정해지지 않아서, 사용자가 직접 프로토콜을 지정해야하는 문제가 있다. 또한 RS-422은 1:1 방식의 Point-to-Point UART를 위해서 사용되고, RS-485는 버스 방식의 연결을 지원할 수가 있지만, 동시에 여러개의 TX가 enable되는 경우에는 TX사이에 고장을 일으킬 수 있어서, 1번에 TX가 1개만 사용되도록 제어할 필요가 있다. 또한 RS-485방식의 버스를 구현할 경우에는 1553B처럼 와전하게 절연이 불가능하므로, 전기적이나 기능적으로 485버스에 문제가 발생할 경우에 절연과 같은 기능이 지원되도록 구현이 되어야 한다. 본 논문에서는 안정적인 485 UART버스 구현을 위한 기술에 대해서 평가하고 분석하도록 하겠다.

• 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.