• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.10a
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• pp.426-431
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• 1997

In this paper, a sensorless realization method is proposed for the magnetic levitation system. Also we design the robust servo controller which based on the two degree-of-freedom-control theory and H$\sub$.inf./ control theory for the system. From time responses, we confirm that the proposed sensorless method can be applied the magnetic levitation system. Also the designed controller has the good disturbance rejection and the reference tracking performance.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.2
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• pp.500-510
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• 1996

This paper presents a new prototype of an engine mount for a passenger vehicle featuring ER(elector-rheological) fluids and piezoactuators. Conventional rubber mounts and various types of passive or semi-active hydraulic engine mounts have their own functional aims on the limited frequency band in the board engine operating frequency range. However, the proposed engine mount covers all frequency range of the engine operation. A mathematical model of the proposed engine mount is derived using the bond graph method which is inherently domain, the ER fluid is activated upon imposing electric field for vibration isolation while the piezoactuator. Computer control electric fluid for the ER fluid H.inf. cotrol technique is adopted for the piezoactuator. Computer simulation is undertaken in order to demonstrate isolation efficiency of the engine mount over wide operating frequency range.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.213-218
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• 1991

A new model which contains the dynamics of the motor system and the kinematics of the timing belt system is derived for an inverted pendulum system in FAPA Lab. Generalized standard compensator configuration(SCC) which contains the variable design parameters Kl, K2, .., K5 is proposed so that any desired design specification can be achieved. The robust controller which has robust property against the influence of sensor noise, system parameter variation and model uncertainty is designed minimizing the H$_{\infty}$-norm of transfer function from exogenous input to controlled output. The method of solving the two Riccati equations in state space and determining the controller uses on iteration method where the unique stabilizing solution to two algebraic Riccati equation must be positive definite and the spectral radius of their product less than .gamma.$^{2}$. Some cases are derived by varying the design parameter for simulation on a digital computer and experimenting the H$_{\infty}$- controller on an analog computer. The design parameters of controller which satisfies the desired control specification is selected on the basis of the simulation result and experimenting. The reasonableness and validity of the simulation and the robustness of the controller is established.d.

• Proceedings of the KIEE Conference
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• 2003.11b
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• pp.111-114
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• 2003

In this paper, we consider the stabilization and $H_\infty$ control of linear systems with static output feedback control. The static output feedback control represents the simplest closed-loop control that can be realized in practice, and, moreover, it is less expensive to be implemented and is more reliable. In spite of its advantages, it is one of the open problems which is not sloved analytically or numerically yet. After decompose the closed-loop system into feedback form, by adopting the small gain theorem, we obtain a sufficient condition for stabilization and a sufficient condition for It control expressed as linear matrix inequalites. Finally, we show the usefulness of our results by a numerical example.

• Water for future
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• v.29 no.1
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• pp.213-220
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• 1996

This paper presents an experimental study on the discharge head of Cherepnov water lifter that was continuously operated with the aid of the siphon. The energy used by the Cherepnov water lifter is derived from the potential energy ofthe water itself. The lifter consists of three interconnected tanks and five pipes, one of which is open and two others are hermetically sealed. The effects of varying operating parameters such as the tank and pipe size, the ratio between head of discharge and drop height were analyzed. As a result, factors that can maximize the efficiency and increase the average delivery rate were indentified. When the ratio between head of discharge and drop height is about 0.5, the efficiency of Cherepnov water lifter is maximized. In order to design the efficient Cherepnov water lifter, the discharge head of the Cherepnov water lifter should be assigned to be twice as much as the drop height. The effect of tank size on the efficiency is less than 5%, while the effect of the pipe size is not negligible. The larger the pipe size is, the more the efficiency increases.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.139-141
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• 1997

In this paper, intervalwise receding horizon controls (IRHCs) are proposed for linear time systems subject to $H_2$ and $H_{\infty}$ problems. Uniform stability conditions are provided for those systems. Under given conditions stability is proved without using an adjoint system. It is also shown that under proposed stability conditions for $H_{\infty}$ problem, $H_{\infty}$-norm bound is satisfied. The results in this paper arc also applicable to periodic systems which belong to the class of time systems.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.1
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• pp.48-56
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• 2008

Nowadays, CMG(Control Moment Gyros) becomes one of the essential actuators for satellite attitude control. The method to define the key requirements of CMG is suggested to avoid CMG's singularity problem for the limited envelope of angular momentum of 2H. Furthermore, the analysis and simulation are carried out to provide a necessary guideline when three CMGs are used for spacecraft control purpose. An improved configuration of redundant four CMG cluster, slightly different from the conventional configuration, is proposed not only to avoid the CMG singularity problem, but to improve agility about roll or pitch-axis.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.123-125
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• 2007

포항가속기연구소가 추진 중인 제4세대 방사광가속기에는 100 PPM급의 클라이스트론 펄스전압 안정도가 요구된다. 이러한 안정도는 PFN(pulse forming network)에 충전되는 전압을 얼마나 정밀하게 제어하는가에 따라서 결정된다. PFN의 최종운전 전압은 deQing circuit에 triggering되는 시점에 따라서 결정된다. DeQing trigger system은 PFN의 충전전압과 기준전압을 비교하여 충전전압이 기준전압보다 커지는 시점에서 charging choke(충전 쵸크)의 2차에 구성된 deQing 회로의 SCR를 트리거 시켜서 충전 쵸크 1차와 2차의 권선비율이 25:1인 충전 쵸크의 2차를 단락시켜 1차에 흐르는 전류를 2차로 빼주어서 PFN 커패시터에 더 이상 충전되지 않게 하는 구조로 되어있다. DeQing circuit에 triggering되는 시점을 정밀하게 제어하기 위하여 PFN 충전전압을 미분하여 그 출력전압에 비례하여 트리거 출력을 지연시키는 기능과 analog 신호를 digital 신호로 변환하는 기능을 사용하였다. 이 논문에서는 deQing 시스템에 관련된 회로 및 시험결과에 대하여 설명하고자 한다.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.959-961
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• 1996

In this paper, we study the modeling and control of Electro-Magnetic Suspension System with 2 Degree Of Freedom. While the previous researchers considered the control of single rail EMS Systems, we consider the control of two rail EMS Systems. We first derive a simple model to represent the dynamics of EMS System with 2 D.O.F., using the Lagrange's method. The nonlinear equations of motion that we derive are shown to be linearizable by coordinate change and nonlinear static state feedback. The nonlinear static state feedback controller is constructed explicitly.

• Clean Technology
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• v.19 no.2
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• pp.156-164
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• 2013

In this study, we analyzed the operational characteristics of a 0.25 MW methanation pilot plant. Isothermal reactor controled the heat released from methanation reaction by saturated water in shell side. Methanation process consisting of isothermal reactor and adiabatic reactor had advantages with no recycle compressor and more less reactors compared with methanation process with only adiabatic reactors. In case that $H_2$/CO ratio of syngas was under 3, carbon deposition occurred on catalyst in tube side of isothermal reactor and the pressure of reactors increased. In case that $H_2$/CO ratio was maintained around 3, no carbon deposition on catalyst in tube side of isothermal reactor was found by monitoring the differential pressure of reactors and by measuring the differential pressure of several of tubes filled with catalyst before and after operating. It was shown that CO conversion and $CH_4$selectivity were over 99, 97%, respectively, and the maximum $CH_4$productivity was $695ml/h{\cdot}g-cat$.