• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.357-359
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• 2006

The electric power system of Kwangyang steel works needs to keep the parallel operation with the system of KOPEC(Korea Electric Power Corporation) for supplying the power with safety. Once it is separated from KOPEC due to an accident, it operates the automatic Mill trip system to prevent huge fluctuating loads from the serious frequency drop. In spite of that, it is recent situations that the continuous growth of electric loads facilitates the frequency drop. Therefore, this paper proposes a model of generator control system so as to quantitatively analyze the response characteristics to the frequency change under the single operation, and also suggests the strategy for minimizing the frequency changes. The simulation results show it is desirable to operate the generators by 3% speed droop and 10% load limiter.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.207-207
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• 2006

We investigated the effects of hydrogen addition to the growth process of SiC single crystal using sublimation physical vapor transport(PVT) techniques. Hydrogen was periodically added to an inert gas for the growth ambient during the SiC bulk growth Grown 2"-SiC single crystals were proven to be the polytype of 6H-SiC and carrier concentration levels of about $10^{17}/cm^3$ was determined from Hall measurements. As compared to the characteristics of SiC crystal grown without using hydrogen addition, the SiC crystal without definitely exhibited lower carrier concentration and lower microplpe density as well as reduced growth rate.

• Transactions on Control, Automation and Systems Engineering
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• v.1 no.2
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• pp.128-133
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• 1999

This paper presents a new delay-dependent robust stabilization condition for uncertain time-delay systems. An algorithm involving convex optimization is proposed to compute a suboptimal upper bound of the delay such that the system can be stabilized by the controller for all admissible uncertainties. It is illustrated by numerical examples that the proposed delay-dependent controller can be less conservative than previous results. It is also shown that the proposed delay-dependent controller can even capture the delay-independent stability of the system, which is not possible with existing delay-dependent results.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.26.5-26
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• 2001

This paper proposes a new approach to identifying the unknown parameters of continuous LTI systems. For parameter identification in continuous-time systems, the Linear Integral Filter (LIF) method generally has been used in the beginning. Especially, one of the most efficient LIF methods in the literature is to use a weighting function satisfying specific three constraints. In high order systems, even though the weighting function satisfies the three constraints, it is impossible to identify the exact parameters of the systems because of information loss arising from a great amount of magnitude differences among the weighting function and its high-order derivatives. This paper, using an LMI technique, shows the limitation in designing the weighting function of the existing methods, and ...

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.27.3-27
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• 2001

In this paper, a robust receding horizon controller for uncertain linear time-varying systems is presented in the dynamic output-feedback form. The existing output-feedback receding horizon controller in the literature is composed of a state observer and a static controller associated with the observer states (similar to LQC control), where the fundamental assumption is that the state observer will supply the exact states as time goes up. The performance of those controllers may be much degraded and even the closed-loop stability may not be guaranteed when the system suffers from disturbances and uncertainties or is time-varying. The proposed controller, which is not necessary to have the state-observer, overcomes such difficulties. Using matrix inequality conditions on the terminal weighting matrix, the closed-loop system stability is guaranteed. Numerical examples are ...

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.161.2-161
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• 2001

To achieve a cooperative work between human and robot, it is thought helpful to estimate the states of human mind, which originates his behavior. In this paper, human mind was considered to modify instinctive desires according to the conditions of external world surrounding the instinct. A simple human mind model was designed so that it finds a balance between instinctive desire and restriction from the external world. The external world is divided into three sub-worlds like subject´s whole body, its partner and concerned periphery. Proposed mind model has three-layers construction. Each of the layer tries to find a balance between desire and restriction from external world. In each layer, the role of finding the balance was expressed by an identical optimal control minimizing a performance index function of quadratic form with a weight factor, which is rearranged and named ...

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.161.5-161
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• 2001

Robots are required to assist our activities in daily life. In this paper, we focus on arm movement to catch moving object as one of important tasks frequently performed by human. We propose an algorithm which enables a robot to perform human-like arm motion to catch a moving object. First we analyze human hand trajectories and velocity profiles to catch an object. From the experimental results, we extract some characteristics in the process of approaching and following a moving object and confirm that these are necessary to realize human-like motion. We then adopt an instantaneous optimal control method which evaluates the error and energy cost at each sampling step, and design two time-varying weight matrices to introduce human characteristic into robot motion. The matrix concerning the error is defined as a time-increasing ...

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.162.6-162
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• 2001

Confocal scanning microscopy (CSM) is an important instrument in a wide variety of imaging applications because of its ability to provide three-dimensional images of thick, volume specimens. The mechanism for two-dimensional beam scanning and optical sectioning has an important roe in CSM as the three-dimensional profiler. This optical sectioning property arises from the use of a point detector, which serves to attenuate the signals from out-of-focus. The intensity profile for the open loop scanning should be matched with its response for the standard. The non-linearity can be minimized with the optical sectioning or the optical probe of the closed loop control. This paper shows the mathematical expression of the light such as the extinction curve in the optical fields of system using AO deflector, the axial/lateral response experimentally when the error sources change, and the methods of optical sectioning. Thorough design of optical sectioner is crucial to the success of CSM in the field ...

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.118.1-118
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• 2001

In this paper, we suggest a new distribution model for a single phase transformer which is different from the existing model which was modeled for only primary parts, but new distribution model is modeled for primary and secondary parts. Using this model, we simulate various faults of the transformer to know how the transfer function vary from the normal one, i.e., the trend of the variation of transfer function. As an another approach, we measure the voltage and current of a three phase transformer while various faults are made at the transformer. From the simulation of the model and experiment, we fine some trends of the variation of transfer function.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.127.2-127
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• 2001

A transformer is one of the most important elements in the power network. Transformer faults could cause costly repairs and be dangerous to personnel. To avoid this, its reliable operation has great significance and, therefore, the diagnosis system of the transformer is necessitated. The dissolved gas-in-oil analysis (DGA) is the worldwide popular method of detecting faults such as a hot spot or partial discharges inside the transformer. DGA, however, is not a reliable technique to identify aging phenomena and mechanical faults including insulation failure, inter-turn short, etc. To overcome the drawbacks of DGA, the transfer function method is used to identify effectively these kinds of the mechanical faults. The transformer has a unique transfer function independent of the shape of the input waveform, which can be evaluated through sweep test. This transfer function changes by winding ...