• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권8호
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• pp.417-425
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• 1999

This paper presents an effective control scheme with the voltage-fed half-bridge series resonant inverter for induction heating system, which is based upon a load-adaptive tuned frequency tracking control strategy using PLL(Phase Locked Loop) and its peripheral control circuits. The proposed control strategy ensures a stable operation characteristics of overall inverter system and ZVS(Zero Voltage Switching) irrespective of sensitive load parameter variations, specially in the non-magnetic materials as well as power regulation. The detail operation principle and the characteristics of inverter system with the proposed control scheme are described and its validity is verified by the simulation and the experimental results for a prototype induction cooking system rated at 1.2kW.

• 대한전기학회논문지:전력기술부문A
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• 제48권6호
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• pp.719-727
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• 1999

A robust position control method of the BLDC motor using a new sliding mode control strategy is presented. The main property of variable structure system(VSS) is that the system response is robust and insensitive to parameter variations and external disturbances in the sliding mode. When using the conventional VSS, generally the reaching phase problem occurs, which cause the system response to be sensitive to parameter variations and external disturbances. Furthermore, the speed of response is relatively slow because the swithching surface is a linear function. In order to overcome these problems, VSS with nonlinear sliding surface eliminating reaching phase is proposed. The validity of the proposed scheme is shown by results of simulations of simulations and experiments for the BLDC motor with variable load.

• 한국지능시스템학회논문지
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• 제11권9호
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• pp.788-792
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• 2001

일반적으로 슬라이딩모드 제어는 외란이나 시스템의 변수변환에 강인한 특성을 가지나, 그 변화의 최대 경계 값을 알아야한다. 그러나, 이 값은 쉽게 얻어질 수가 없다. 퍼지 논리는 잘 정의되어 있지 않거나 복잡한 시스템의 제어기 설계에 효과적인 방법을 제시하나, 과도응답을 미리 결정할 수가 없다. 본 논문에서는 두 이론의 장점을 결합하여 새로운 제어 알고리듬을 제시한다. 최적의 퍼지변수 값을 결정하기 위하여 적응이론을 도입한다. 마지막으로 제안한 제어 알고리듬의 타당성을 살펴보기 위하여 수치적인 예를 가변길이진자시스템에 적용한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 A
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• pp.219-223
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• 1995

This paper deals with the robust control system for parameter variations, fast responses and load torque variations. Frist, fuzzy-sliding adaptive control be used to. Fuzzy-sliding adaptive control is good at fast response. Second, there are many requests for selecting freely the moment of inertia, even though moment of inertia is determined with the materials, structure, shape, and size of the motors. Therefore we developed an inertia-lowering control system that uses torque observer to reduce the moment of inertia. Finally, using torque observer, torque control is done so as to compensate load torque. Consequently, the proposed system verified the superiority through the simulations using MATLAB.

• Nuclear Engineering and Technology
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• 제51권3호
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• pp.867-876
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• 2019

Second harmonic generation using nonlinear ultrasonic waves have been shown to be an early indicator of possible fatigue damage in nuclear power plant components. This technique relies on measuring amplitudes, making it highly susceptible to variations in transducer coupling and instrumentation. This paper proposes an experimental procedure for in-situ surface wave nonlinear ultrasound measurements on specimen with permanently mounted transducers under high cycle fatigue loading without interrupting the experiment. It allows continuous monitoring and minimizes variation due to transducer coupling. Moreover, relations describing the effects of the measurement system nonlinearity including the effects of the material transfer function on the measured nonlinearity parameter are derived. An in-situ high cycle fatigue test was conducted using two 304 stainless steel specimens with two different excitation frequencies. A comprehensive analysis of the nonlinear sources, which result in variations in the measured nonlinearity parameters, was performed and the effects of the system nonlinearities are explained and identified. In both specimens, monotonic trend was observed in nonlinear parameter when the value of fundamental amplitude was not changing.

• 전기학회논문지
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• 제60권5호
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• pp.977-983
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• 2011

This paper proposes a new adaptive speed controller to achieve a robust speed control of a permanent magnet synchronous motor(PMSM). The proposed adaptive regulator does not require any information on the motor parameter and load torque values, so it is very insensitive to model parameter and load torque variations. Also, the stability of the proposed adaptive control system is proven. To validate the robustness of the proposed adaptive speed controller, both simulation and experimental results are provided under motor parameter and load torque variations. It is clearly demonstrated that the proposed adaptive regulator can accurately control the speed of permanent magnet synchronous motors.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.75.3-75
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• 2001

This paper addresses the design of State-feedback Robust Guaranteed-Cost Controllers with controller gain variations. Since the unstructured uncertainty is the most dominant uncertainty in the modeling of the plant, the plant is assumed to have the unstructured uncertainty. It is necessary to take the controller parameter perturbation into consideration when we design the robust controller. Otherwise, the resulting controller may show the fragility property. That is to say, the extremely small controller parameter variation may result in the instability of the overall closed-loop system. Therefore, the design purpose is that the maximum performance index is guaranteed in the presence of the unstructured plant uncertainty and controller parameter variations ...

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 B
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• pp.493-495
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• 1998

Robust design is one method to make manufacturing less sensitive to manufacturing process. Also it is cost effective technique to improve the quality process. This method uses statistically planned experiments to vary settings of important process control parameters. In this paper we apply fuzzy optimization and fuzzy logic system to robust design concept. First a method which uses fuzzy optimization in obtaining optimum settings by measured data from experiments will be presented. Second, fuzzy logic system is made to reduce experiments using experiments results consisted with key control parameter combinations. Then optimum parameter set points are obtained by the descrebed first fuzzy optimization method after prediction the results of each parameter combinations considering each control parameter variations by nonsingleton fuzzy logic system concept.

• 한국지능시스템학회논문지
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• 제13권1호
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• pp.63-69
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• 2003

가변구조제어는 외란과 시스템의 변수 변화에 대해 강인한 특성을 가지며, 그 상한값만 안다면 체계적이고도 쉽게 제어기를 설계할 수 있는 특성이 있다. 그러나 외란과 시스템의 변수 변화의 상한값을 알기란 그렇게 쉽지만은 않다 이에 반해 퍼지제어기는 외란과 변수 변화에 대한 정확한 정보가 없는데도 불구하고 제어기 설계에 있어서 효과적인 방법을 제공한다. 따라서 퍼지제어기와 가변구조제어기가 가지는 장점들을 결합하는 연구가 진행되어져 왔다. 일반적으로 가변구조제어기는 리칭페이저가 존재하며, 이 구간에서는 강인성을 보장학 수가 없다. 본 논문에서는 적응 알고리듬을 사용한 전 구간이 강인한 리칭페이저가 존재하지 않는 적응퍼지가변구조제어기를 설계하였다. 제안된 제어 알고리듬을 사용하여 BLDC 전동기의 위치제어기를 설계하였으며, 실험을 통하여 그 타당성을 입증하였다.

• 수산해양기술연구
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• 제30권4호
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• pp.320-328
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• 1994

In 1980 s to 1990 s the marine propulsion diesel engines have been developed into lower speed and longer stroke for the enegy saving (small S.F.O.C). As these new trends the conventional mechanical-hydraulic governors were not adapted to the new requirements and the digital governors have been adopted in the marine use. The digital governors usually use the control algorithms such as the PID control, optimal control, adaptive control and etc. While the engine has delay time and parameter variations these control algorithms have difficulty in considering the stability and the robustness for the model uncertainty. In this study, the $H_{\infty}$ controller design method are applied in order to design the feedback controller K(s) to the speed control of the low speed marine diesel engine, and the two-degree-of-freedom control system is constituted with $H_{\infty}$controller. By comparison of responses of the two-degree-of-freedom control system under the delay time and parameter variations is confirmed.