• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 16-17 Oct. 1987
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• pp.139-144
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• 1987

The problem of process(Sensor) fault management in Observer Based Control System are considered and structures of Fault Tolerant Observer based Control Systems (FMCS) that function well in the face of the faults are proposed. The FTOCSs include detection logic unit and an additional observer driven by residuals of primary observer and estimate estimation errors of primary observer and fault variables. Since the FTOCSs have the ability to detect and accomodate the faults the original control objectives can be accomplished without considerable control performance deterioration even in the faulty environments. Therefore, the Proposed FMCSs can effectively be used for enhancing the functional reliability of the Observer Based Control Systems.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 춘계학술대회 논문집
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• pp.582-587
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• 2011

Acoustic Emission(AE) is widely used for early detection of faults for rotating machinery in these days because of its high sensitivity. AE signal has to need for transferring to low frequency range for the spectrum analysis included the fault mechanism. In transferring process, we lose a lot of fault information caused by unusable signal processing method. Discrete Wavelet Transform(DWT) is a method of signal processing for AE signatures, but the pattern of its mother function is not optimized with AE signals. So, we can lose the fault information when we want to use the DWT for AE signal. Therefore, in this paper, we will propose a novel pattern for DWT mother function, which is optimized with AE signals. And it will be applied to compare the results of DWT by daubechie and novel pattern.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.35-38
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• 2008

This paper develops an aero engine LPV mathematical model to exactly describe aero engine dynamic process characteristics, eliminate the effect of modeling error. Design FDF with eigenstructure assignment. The simulation results of turbofan engine control system sensor fault show that this method has good performance in focusing discrimination in fault signal with modeling eror, enhancing the robustness to unknown input, detecting accuracy is high and satisfiying real-time requirement.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2004년도 추계 종합학술대회 논문집
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• pp.314-317
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• 2004

네트워크 및 소프트웨어 하부구조의 진보에 의해 이형의 컴퓨팅 자원 집합으로 구성된 환경에서 그리드 컴퓨팅 기술은 확산되고 있다. 그리드 컴퓨팅은 광대역으로 연결되어진 분산 컴퓨터들의 조정에 의한 사용을 요구한다. 그리드 컴퓨팅을 위한 다양한 시스템과 그리드 응용 서비스의 증가에 따라 그리드 운영환경은 네트워크 분리 및 노드 결함 등에 의해 높은 결함율을 가질 수 있다. 결함 검출은 그리드 응용 시스템의 강건성을 위해 시스템 설계 및 구현시의 필수적인 요소이다. 본 논문에서는 낮은 네트워크 트래픽 환경에서 높은 신뢰성 정공을 위한 OGSA(Open Grid Service Architecture) 기반의 자원 결함 검출 서비스를 제안한다.

• 한국지능시스템학회논문지
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• 제13권5호
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• pp.600-605
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• 2003

주성분 분석은 공정의 모니터링과 고장진단을 위한 유용한 방법으로 알려져 있으며 일반적으로 잔차와 주성분의 해석을 통하여 고장의 원인을 분류하고 있다. 대규모 공정에서는 이러한 방법이 적용상의 한계를 가지고 있다. 본 논문에서는 보다 향상된 고장진단을 위해 주성분 분석에 FCM-기반 고장 진단 알고리즘을 결합하였고 Two-tank 시스템을 이용하여 주성분 분석을 이용한 FCM-기반 고장진단 알고리즘의 구현하여 적용하였다.

• 대한전자공학회논문지
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• 제24권1호
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• pp.28-34
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• 1987

As a means of improving the reliability of a process control system, a FTCS(Fault Tolerant Control System) is designed and applied to the boiler controller of a thermal power plant. The proposed FTCS has capabilities of fault detection and diagnosis as well as back-up control and bumpless switching. A prototype of FTCS is implemented on an IBM PC as an add-on system and it is experimentally verified by using a boiler process simulator together with simplified analog controllers and a switching unit that an one-fold fault is detected in real time and back-up controller takes over the role of the original controller, controlling the faulty loop.

• 전기학회논문지
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• 제56권5호
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• pp.834-840
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• 2007

A generator plays an important role in transferring an electric power to power system networks. The generator protection systems in Korea have been imported and operated through a tum-key from overseas entirely. Therefore, a study of the generator protection field has in urgent need for a stable operation of the imported goods, and for preparation of next generation protection system. The paper describes the fault detection algorithm using WT(Wave!et Transform) of currents for a generator protection. The fault current signals after executing a terminal fault modeling collect using a MA TLAB package, and calculate the wavelet coefficients through the process of a multi -level decomposition (MLD). The proposed algorithm for a fault detection using the Daubechies WT (wavelet transform) was executed with a C language for the command line function and for the real time realization after analyzing MATLAB's graphical interface. The advanced technique had complemented the defects of a DFT by applying a Daubechies WT. and had improved faster a speed and more accurate of fault discriminant than a conventional DFR.

• Journal of Welding and Joining
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• 제28권4호
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• pp.81-86
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• 2010

In resistance spot welding, regardless of the optimal condition, bad weld quality was still produced due to complicated manufacturing processes such as electrode wear, misalignment between the electrode and workpiece, poor part fit-up, and etc.. Therefore, the goal of this study was to measure the process signal which contains weld quality information, and to develop the process fault monitoring system. Welding force signal obtained through variety experimental conditions was analyzed and divided into three categories: good, shunt, and poor fit-up group. And then a monitoring algorithm made up of an artificial neural network that could estimate the process fault of each different category based on pattern was developed.

• 한국시뮬레이션학회논문지
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• 제20권4호
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• pp.67-79
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• 2011

본 연구에서는 시계열 공정데이터 관리를 위한 모델모수 기반 이상 탐지방법을 제안한다. 일반적인 공정관리에 널리 쓰이는 전통적인 통계적 관리기법의 관리도(SPC chart)는 측정되는 데이터가 특정 분포를 따르며 상관관계가 없는 상황을 가정한다. 따라서 공정데이터 형태가 시계열데이터와 같이 특정분포를 따르지 않고, 자기상관관계를 갖는다면 전통적인 관리도로는 관리에 한계를 보인다. 본 연구는 시계열을 따르는 공정의 이상을 탐지를 위한 MPBC(Model Parameter Based Control-chart) 방법을 제안한다. 제안된 MPBC는 시계열공정을 모델링하고, 모델모수의 변화를 감지하여 공정의 이상을 탐지하는 방법이다. 시계열 공정은 ARMA(p,q) 모델을 가정하며, RLS(Recursive Least Square)를 이용하여 시계열 모델의 모수를 추정하고, 추정된 모수를 $K^2$관리도로 관리한다. 제안된 방법은 기존 알고리즘과 비교하여 시계열 공정 변화 탐지에 우수한 성능을 보였으며 시계열 데이터에 있어서 보다 효율적인 공정관리 방향을 제시한다.

• 한국경영과학회지
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• 제36권1호
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• pp.39-55
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• 2011

Process monitoring has been emphasized for the monitoring of complex system such as chemical processing industries to achieve the efficiency enhancement, quality management, safety improvement. Recently, ICA (Independent Component Analysis) based MSPC (Multivariate Statistical Process Control) was widely used in process monitoring approaches. Moreover, DICA (Dynamic ICA) has been introduced to consider the system dynamics. However, the existing approaches show the limitation that their performances are strongly dependent on the statistical distributions of control variables. To improve the limitation, we propose a novel approach for process monitoring by integrating DICA and LOF (Local Outlier Factor). In this paper, we aim to improve the fault detection rate with the proposed method. LOF detects local outliers by using density of surrounding space so that its performance is regardless of data distribution. Therefore, the proposed method not only can consider the system dynamics but can also assure robust performance regardless of the statistical distributions of control variables. Comparison experiments were conducted on the widely used benchmark dataset, Tennessee Eastman process (TE process), and showed the improved performance than existing approaches.