• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.2
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• pp.273-280
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• 1999

This paper presents the design and implementation of circuit analyzer system for the convenient troubleshooting and diagnosis of the electronics appliance using the curve tracer technology of analog signature analysis. The circuit analyzer provides advanced troubleshooting capabilities to simplify testing newer technology components such as CMOS and MOS circuits, its built-in pulse generator lets thoroughly troubleshoot gate-fired devices such as SCRs, TRIACs and optocouplers. The circuit analyzer while the power to the circuitry testing is turned of, so that avoid an accidental short that could cause further damage, its allow to analyze the impedance state of a solid-state component, which makes it perfect for finding leakage or substrate damage that has brought a system or PCB down prematurely. Because it can compare suspect components to known-good equivalents, it's verified the ideal application for troubleshooting when documentation is missing or incomplete.

• Proceedings of the KIPE Conference
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• 2017.11a
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• pp.103-104
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• 2017

영구자석 전동기는 전력 밀도가 높고 효율이 좋은 특징으로 견인, 의료, 군사 분야 등 다양한 산업 분야에서 사용되고 있다. 이러한 분야에서 사용되는 전동기 구동 시스템은 높은 신뢰성이 요구되므로 인버터에서 발생하는 전력 반도체 스위치 고장을 빠르게 감지해야한다. 본 논문에서는 제어기 상전압 지령과 추정된 상전압 사이의 오차를 통해 전력 반도체 개방 고장을 감지하고 진단하는 방법을 제시하였다. 제안된 방법은 추가적인 측정 회로 없이 제어기 내부 값을 사용하여 개방 고장을 감지하고 개방된 스위치를 진단할 수 있다. 특히 부하 변동을 고려한 감지 방법을 제안하여 고장 감지의 신뢰성을 개선한다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.6
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• pp.40-51
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• 2009

To analyze influences under open faults in switching devices of the PWM inverter and under the isolation between the inverter and motor terminal, a faulty model for the inverter-driven permanent magnet synchronous motor is presented. Even though the conventional dq motor model obtained through the transformation of phase voltage model is widely used to analyze and control AC motor, it can not be used under open faults in switching devices since the 3-phase balanced condition is no longer hold under the open fault and it is not easy to obtain motor input voltages in open phase from the pole voltage. To deal with this problem, a faulty model for an inverter-driven permanent magnet synchronous motor is derived by using the line voltage of motor according to switch open, which can be effectively used for performance evaluation of the diagnostic algorithm. The validity of the proposed faulty model is verified through comparative simulations and experiments using DSP TMS320F28335.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.6
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• pp.526-532
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• 2007

This paper considers a fault tolerant control problem for a spacecraft using reaction wheels. Faults are assumed to be inherent to only actuators(reaction wheels) and a control algorithm to accommodate actuators' faults is proposed. An attitude control loop includes an angular velocity control loop. The time delay control method is used to make a spacecraft follow the command angular velocity and to accommodate actuators' faults. A stability condition for the proposed algorithm is derived and the performance is demonstrated by computer simulations.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.41 no.4
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• pp.29-37
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• 2004

This paper provides a reliable H$_{\infty}$ state feedback controller design method for delayed singular systems with actuator failures occurred within the prescribed subset. The sufficient condition for the existence of a reliable H$_{\infty}$ controller and the controller design method are presented by linear matrix inequality(LMI), singular value decomposition, Schur complements, and changes of variables. The proposed controller guarantees not only asymptotic stability but also H$_{\infty}$ norm bound in spite of existence of actuator failures. Since the obtained sufficient condition can be expressed as an LMI fen all variables can be calculated simultaneously. Moreover, the controller design method can be extended to the problem of robust reliable H$_{\infty}$ controller design method for singular systems with parameter uncertainties, time-varying delay, and actuator failures. A numerical example is given to illustrate the validity of the result.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.510-511
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• 2017

In this paper, we have studied to minimize the lifetime and fault occurrence of LED fixtures, which have a short lifetime and frequent faults. In the current LED chip, the lifetime is semi-permanent, but compared to the lifetime of the LED chip, Drivers do not last long. In recent years, low-priced LED illuminators such as those from China have entered the market, and many consumers are perceiving LED illuminators. In order to solve these problems, we designed an LED illuminator of 25W class by using AC Direct IC, which has a longer lifetime than the conventional driver, by removing the electrolytic capacitor in the LED driving driver which is the cause of the failure.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.2
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• pp.98-106
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• 2013

This paper proposes fault tolerant control laws using sliding mode control and adaptation laws for a satellite with reaction wheel faults. Considering system parameter errors and faults uncertainties in the dynamics of satellite, the control laws were designed. It was assumed that only reaction wheel failures occurred as faults. The reaction wheel faults were reflected in the multiply form. Because the proposed control laws satisfy the Lyapunov stability theorem, the stability is guaranteed. Through computer simulation, it was assured that the proposed adaptive sliding mode controller has a better performance than the existing sliding mode controller under unstable angular rates.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.79.2-79.2
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• 2010

FCEV(Fuel Cell Electric Vehicle)는 연료전지스택의 각 셀에서 반응하는 화학에너지를 전기에너지로 변환하여 차량을 구동하는 시스템이다. 이러한 연료전지 셀이 정상적인 발전이 되지 않을 경우 비정상적인 전압이 발전되고 이것을 방치한다면 연료전지 스택의 영구적인 고장을 야기할 수 있다. 이를 방지하기 위해 SVM(Stack Voltage monitor) 제어기는 각 셀의 전압을 측정하고 그 정보를 상위 제어기인 FCU(Fuel cell Control Unit)에 전달한다. 이에 FCU는 연료전지스택의 고장을 운전자에게 알리고 연료전지스택의 발전을 멈추게 한다. 기존에 SVM 제어기는 각 셀마다 분압저항을 통하여 측정하며 이 전압의 차를 이용하여 셀 전압을 계산하는 방식이었다. 이는 상위 셀로 갈수록 오차가 커지는 문제가 있고 다수의 CPU 및 DC/DC 컨버터가 적용이 필요하여 복잡한 구성과 가격이 높은 문제가 있었다. 이러한 문제점을 해결하기 위하여 cell monitoring IC를 적용하였고 좀 더 정밀한 측정과 간단한 인터페이스를 구성할 수 있었다. 본 연구에서는 기존 SVM 제어기보다 안정되고 정밀한 SVM 제어기의 개발에 대해 기술하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.9
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• pp.975-980
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• 2007

Air-operated valve is one of principal valves that are used to control fluid flow in nuclear power plants. A periodic diagnosis for the safety of power plants is necessary. But there are many difficulties such as economic loss caused by income of high cost devices and a matter hard to deal with users. In this study, we developed the diagnostic system that users of power plants are easy to handle. The diagnostic system is composed of database module, diagnosis test module and analysis module.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.5
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• pp.389-397
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• 2021

The control characteristics after the failure of the control moment gyros, the actuators for satellite attitude control, were analyzed. In particular, the situation where one out of four failed was considered. For the most commonly used pyramids and box-90 structures, the singularities and singular surfaces after failure were analyzed and compared. Dynamic equations for the process of reducing the wheel speed after the failure were derived. The process of stabilizing the angular velocity of a satellite while absorbing the momentum of the faulty module by the three normal modules was analyzed. For singular shapes, the remaining CMGs may be locked or excessively shake. The authors proposed that it can be prevented by rearranging the gimbal angles.