• 제어로봇시스템학회논문지
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• 제9권8호
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• pp.610-615
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• 2003

This paper proposes a nonlinear virtual coupling fur haptic interface, which offers better performance while maintaining stability of the system. The nonlinear virtual coupling is designed based on a human response model. This human response model exploits delay between the human Intention and the actual change of arm impedance. The proposed approach provides with less conservative constraints for the design of stable haptic interface, compared with the traditional passivity condition. This allows increased performance that is verified through experiments.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1995년도 Proceedings of the Korea Automation Control Conference, 10th (KACC); Seoul, Korea; 23-25 Oct. 1995
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• pp.191-194
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• 1995

This paper evaluates the influences of sex on the human emotions while coexisting with robots. When we consider human vision, robot's motion is the most important parameter which influences human emotions and must be well controlled for males and females emotions. On the other hand, when we consider human touch of sense, which is effective for cooperation transmitting mutual forces, the softness of robot is an important parameter for human emotions and must be also well controlled for males and females emotions. From these points of view, at first, we evaluate robot's motion under four different shapes of velocity pattern while handing over a cup to humans. Second, we evaluate robot's softness realized by impedance control. From the first experiment, we concluded that the conditions of choosing an adequate maximum velocity value and locating the velocity peak at the center or the first half of the duration are necessary for male's emotions. In addition, the smooth velocity decrease in the last part of the velocity pattern's duration is desired for female's emotions. From the second experiment, we concluded that females prefer lighter values of virtual impedance characteristics than males and any small increase on the heaviness of virtual impedance values is followed by the negative exponential change on human emotions.

• 제어로봇시스템학회논문지
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• 제9권8호
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• pp.585-591
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• 2003

A virtual force is generated and fed back to the operator to make the teleoperation more reliable, which reflects the relationship between a slave robot and an uncertain remote environment as a form of an impedance. In general, for the teleoperation, the teleoperated mobile robot takes pictures of the remote environment and sends the visual information back to the operator over the Internet. Because of the limitations of communication bandwidth and narrow view-angles of camera, it is not possible to watch certain regions, for examples, the shadow and curved areas. To overcome this problem, a virtual force is generated according to both the distance between the obstacle and the robot and the approaching velocity of the obstacle w.r.t the collision vector based on the ultrasonic sensor data. This virtual force is transferred back to the master (two degrees of freedom joystick) over the Internet to enable a human operator to estimate the position of obstacle at the remote site. By holding this master, in spite of limited visual information, the operator can feel the spatial sense against the remote environment. It is demonstrated by experiments that this collision vector based haptic reflection improves the performance of teleoperated mobile robot significantly.

• 한국멀티미디어학회:학술대회논문집
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• 한국멀티미디어학회 2001년도 추계학술발표논문집
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• pp.260-264
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• 2001

This paper presents virtual reality using 6-DOF Haptic interface. It is proposed reappearance of force using 6-DOF Haptic device that was designed by previous studies and 3D image considered time delay. The performance of conventional control is excellent in the case of the exactly known dynamic model of the robot, but degrades seriously as the uncertainty of the model increases. The virtual reality using 6-DOF Haptic interface is presented here to overcome such that, and verified through the experiment.

• 전력전자학회논문지
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• 제7권5호
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• pp.499-508
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• 2002

본 논문에서는 N.1 모듈형 UPS 시스템의 병렬운전을 위해 기존에 사용된 부하분담용 신호선을 제거하고 독립적인 운전을 수행하는 새로운 형태의 wirelss 병렬제어 알고리즘을 제안하고자 한다. 제안된 제어시스템은 기존 방식이 갖는 센싱 노이즈나 상호간섭에 의한 문제를 제거할 수 있다. 또한 wireless방식의 단점을 보완하기 위해 인버터간 불평형요소 제거 알고리즘을 적용하여 무효전력편차의 발생을 최소화하는 구조를 가지며, 시스템의 불안정한과도특성을 완충하는 가상의 임피던스를 삽입하여 과도순환전류를 저감하는 방식이 적용되었다. 제안된 알고리즘의 타당성을 검증하기 위해 시뮬레이션 결과를 제시하였다.

• 한국전자파학회논문지
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• 제12권7호
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• pp.1139-1146
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• 2001

일차원 매질에 대한 역산란법을 이용하여 테이퍼형 임피던스 정합선로를 설계한다. 역산란법으로 유전율 분포를 추정하는 과정에서 오타를 줄이기 위하여 위상 보정인자(PCF: Phase Compensation Factor)를 도입한다. 설계하고자 하는 정합선로와 동일한 반사특성을 갖는 가상(virtual) 일차원 유전체의 유전율 분포를 추정하여 정합선로를 합성한다. 이 설계법은 등가회로에 대한 회로망 이론을 적용하지 않고 임의의 대역 특성을 갖는 정합선로를 설계할 수 있다. 주파수 영역의 반사계수를 사용함으로써 시간 영역의 반사계수를 사용하는 설계법에서 필연적으로 나타나는 오차를 피할 수 있다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 D
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• pp.2693-2695
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• 2004

Recently A virtual environment provides patient with stimuli which arouses phobia, and exposing to that environment makes him having ability to over come the fear. ECG and HRV are used in most virtual reality system. GSR is electrical impedance of biological tissues and the changes in impedance accompanying physiological activity. GSR is better than ECG or HRV for explaining mental states in other study. In this study, we will analysis GSR signal when a acrophobia patient and a normal is on high floor.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2019년도 전력전자학술대회
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• pp.342-343
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• 2019

This paper explores the power distribution problem of parallel-connected inverter system which supplies auxiliary power for railway facilities. We propose a droop control method which facilities power distribution and restrain of voltage drop by tracking the average power control command by adjusting the virtual impedance. The performance of proposed droop method is verified by the PSIM simulation.

• Journal of Power Electronics
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• 제19권6호
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• pp.1467-1476
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• 2019

Grid unbalanced faults can cause core saturation of power transformer and produce lower-order harmonics. These issues increase the electrical stress of power electronic devices and can cause a tripping of an entire HVDC system. In this paper, based on the positive-sequence and negative-sequence impedance model of a VSC-HVDC system as seen from the point of common connection (PCC), the resonance problem is analyzed and the factors determining the resonant frequency are obtained. Furthermore, to suppress over-voltage and over-current during resonance, a novel method using a virtual harmonic resistor is proposed. The virtual harmonic resistor emulates the role of a resistor connected in series with the commutating inductor without influencing the active and reactive power control. Simulation results in PSCAD/EMTDC show that the proposed control strategy can suppress resonant over-voltage and over-current. In addition, it can be seen that the proposed strategy improves the safety of the VSC-HVDC system under unbalanced faults.

• 대한기계학회논문집B
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• 제27권6호
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• pp.714-725
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• 2003

The theory of the current-type electromagnetic flowmeter for a high temporal resolution was developed for two-phase flow measurements. To predict the output of the current-type flowmeter, the three-dimensional virtual potential distribution C and the newly introduced flow pattern coefficient f were derived and computed. The output of flowmeter depends on the liquid conductivity (sensitive to temperature) and flow configurations of the two-phase flow with the sinusoidal excitation over 100 Hz. The flow pattern coefficient was specially devised to separate the dependency on the flow configuration of the two-phase flow from that on the liquid conductivity which can be expressed with the calibration of single-phase flow. Using the finite difference method, the three-dimensional virtual potential distributions were computed for the electrode of finite size. By taking derivative of the virtual potential, the weight functions were evaluated and compared with existing analytic series solution for the point-electrode. There was a reasonable correspondence between the present and existing results. In addition, the flow pattern coefficients were evaluated for annular flows with various film thicknesses, and compared with the experimental results by the impedance spectroscopy. The numerical results agreed well with the experimental data.