• Journal of the Korean Society for Precision Engineering
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• v.23 no.4 s.181
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• pp.83-90
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• 2006

A robot manipulator is usually operated in two modes: free and constrained motion modes, depending on whether the robot is in contact with an environment or not. At the moment of contact, an impact occurs and can exert harmful effects to the robot or the object. In case of teleoperation, since a user may give an inadequately excessive velocity command to the slave due to insufficient visual information, the robot nay collide the object with an excessive speed and it possibly deteriorates the robot's performance causing vibrations and at worst, shortens its lifetime by its fracture. In this article, a new algorithm is proposed by introducing a command signal modification method on the basis of impedance control and validity of the proposed algorithm is demonstrated by performing simulations and experiments.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.305-307
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• 2003

This paper presents an apparent impedance calculation procedure for distance relaying of transmission line involving FACTS (Flexible AC Transmission System) devices, particularly the UPFC (Unified Power Flow Controller), between Kangjin and Jangheung in Korea. With the changes of UPFC's parameters, the measurement and protective range (trip boundaries) of the adaptive distance relay can also be changed. So, it is the most important part in the field of system protection to analyze the operating characteristic of relaying system. The presence of UPFC significantly affects the trip boundaries which are also adversely affected by fault resistance combined with remote end infeed. This paper presents the apparent impedance calculations and the distance relay setting characteristics for faults involving the UPFC in the KEPCO system.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.454-455
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• 2018

The impedance of an underwater acoustic transducers constituting a multi-channel array structure could be changed in real time by various transmission modes. A power amplifier for driving the transducers usually use a voltage control method, so the transducer and power amplifier may be damaged by over-power due to changeable load conditions. Therefore, the drive controller of the power amplifier should have the function of limiting the power. This paper propose the new voltage control method for limiting the driving power of transducers with variable impedance characteristics.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.501-505
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• 2001

The parallel operation system of UPS is used to increase reliability of power source at critical load. But parallel UPS system has a few defects, impedance is different from each other and circulating current occurs between UPSs, due to line impedance and parameter variation, though controlled by the same synchronization signal. According to such characteristic of parallel UPS, balanced load-sharing control is the most important technique in parallel UPS operation. In this paper, a novel power deviation compensation algorithm is proposed. it is composed of voltage controller to compensate power deviation that be calculated by using active and reactive current deviation between inverters on synchronous d-q reference frame.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.409-412
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• 2000

A high performance EEG signal measurement system is fabricated. It consists of high precision pre-amplifier and auto identification bandwidth unit. High precision pre-amplifier is composed of signal generator, signal amplifier with a impedance converter, body driver and isolation amplifier. The pre-amplifier is designed for low noise characteristics, high CMRR, high input impedance, high IMRR and safety, Auto identification bandwidth unit is composed of AD-converter and PIC micro-controller for real time processing EEG signal. The performance of EEG signal measurement system has been shown the classified bandwidth through the clinical demonstrations.

• Journal of Sensor Science and Technology
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• v.20 no.4
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• pp.243-248
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• 2011

The purpose of this study is to develop a sensing system to measure the capacitance of a pre-developed engine oil deterioration detection sensor integrated with an oil filter. To measure the capacitance of engine oil in the sensor, it is used the way measuring the electric charging time in a capacitor by impressing DC volt. This method has merits on cost and signal stability. The measured capacitance is compensated by comparison with the one measured by an impedance analyzer. Also, using the dielectric constant gained by an impedance analyzer, the calculating equation of the dielectric constant of engine oil related with the currently developed sensor is decided. Finally, the degradation degree of engine oil is estimated according to the change rate of dielectric constant between green oil and used oil. The newly developed personal controller is to control a series of the processes.

• Proceedings of the Acoustical Society of Korea Conference
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• 1994.06a
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• pp.764-769
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• 1994

The impedance of an electro-acoustic transducer can be controlled by motional feedback, and the noise in a duct can be reduced actively by adjusting the impedance using an additional sound. In this paper, two approaches for active noise control using motional feedback (MFB) loudspeaker are described. First configuration uses an external sensor to pickup of source directly. In this configuration, the adaptation of controller is necessary to compensate the change of transfer function from noise source to control poing. The second configuration uses a new adaptive algorithm specialized for peridic noise. Because this configuration does not require any reference input and the error sensor couples very tightly with control loudspeaker, this MFB system itself is independent of the duct condition. No microphone are required in both configurations, so that a more reliable and stable active control system can be realized under severe conditions such as high pressure, high temperature, dust, flow and so on.

• KIEE International Transactions on Power Engineering
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• v.4A no.1
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• pp.1-5
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• 2004

The model of a power system with load dynamics is studied by investigating qualitative changes in its behavior as the reactive power demand at a load bus is increased. The load is created using induction motors parallel with the constant power and constant impedance load. As the load increases, the system experiences various bifurcations such as sub critical and supercritical Hopf, period-doubling and saddle-node bifurcation. The latter may lead the system to voltage collapse. A nonlinear controller is used to control the subcritical Hopf bifurcation and hence mitigate voltage collapse. It is applied to the KEPCO (Korean Electric Power Company) system to demonstrate its validity.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.5
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• pp.220-225
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• 2006

Arc Fault Current is an electric discharge which is occurred in two opposite electrode. In this paper, AFCI(arc fault circuit interrupter) is designed for the interruption of arc fault current which is occurred in the local electric network. This arc is one of the main causes of electric fire. Arc fault in electrical network has the characteristics of low current, high impedance and high frequency. Conventional arc fault circuit interrupter does not have the arc current interrupt function. Hence, Arc current controller is designed for the interruption of arc fault current which has the modified arc characteristics.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.220-222
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• 2001

This paper represents impedance calculation of the distance relay using PSCAD/EMTDC software for transmission line involving the UPFC (Unified Power Flow Controller) device, which is the most vigorous component of FACTS. The presence of the UPFC significantly affects the line parameters of transmission system, which are also influenced by the distance relay setting. Moreover depending on the UPFC location and its parameters, zones of setting the distance relay will be changed. The presence of the UPFC in the fault loop affects both voltage and current seen by relay. Therefore, the distance relay should be taken into account the variable injected voltage of the UPFC.