• 제어로봇시스템학회논문지
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• 제10권5호
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• pp.450-457
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• 2004

In this research, the automatic synthesis of knowledge models is proposed. which are the basis of the methods using qualitative models adapted widely in fault diagnosis and hazard evaluation of chemical processes. To provide an easy and fast way to construct accurate causal model of the target process, the Role-Behavior modeling method is developed to represent the knowledge of modularized process units. In this modeling method, Fault-Behavior model and Structure-Role model present the relationship of the internal behaviors and faults in the process units and the relationship between process units respectively. Through the multiple modeling techniques, the knowledge is separated into what is independent of process and dependent on process to provide the extensibility and portability in model building, and possibility in the automatic synthesis. By taking advantage of the Role-Behavior Model, an algorithm is proposed to synthesize the plant-wide causal model, Fault-Causality Graph (FCG) from specific Fault-Behavior models of the each unit process, which are derived from generic Fault-Behavior models and Structure-Role model. To validate the proposed modeling method and algorithm, a system for building FCG model is developed on G2, an expert system development tool. Case study such as CSTR with recycle using the developed system showed that the proposed method and algorithm were remarkably effective in synthesizing the causal knowledge models for diagnosis of chemical processes.

• Advances in aircraft and spacecraft science
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• 제4권1호
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• pp.53-64
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• 2017

Aerospace Launch Vehicles (ALV) are generally designed with high reliability to operate in complete security through fault avoidance practices. However, in spite of such precaution, fault occurring is inevitable. Hence, there is a requirement for on-board fault recovery without significant degradation in the ALV performance. The present study develops an advanced fault recovery strategy to improve the reliability of an Aerospace Launch Vehicle (ALV) navigation system. The proposed strategy contains fault detection features and can reconfigure the system against common faults in the ALV navigation system. For this purpose, fault recovery system is constructed to detect and reconfigure normal navigation faults based on the sliding mode observer (SMO) theory. In the face of pitch channel sensor failure, the original gyro faults are reconstructed using SMO theory and by correcting the faulty measurement, the pitch-rate gyroscope output is constructed to provide fault tolerant navigation solution. The novel aspect of the paper is employing SMO as an online tuning of analytical fault recovery solution against unforeseen variations due to its hardware/software property. In this regard, a nonlinear model of the ALV is simulated using specific navigation failures and the results verified the feasibility of the proposed system. Simulation results and sensitivity analysis show that the proposed techniques can produce more effective estimation results than those of the previous techniques, against sensor failures.

• 한국컴퓨터정보학회논문지
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• 제21권10호
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• pp.125-133
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• 2016

In this paper, we propose a real-time fault monitoring and dual system design of the countdown time-generating system, which is the main component of the mission control system. The countdown time-generating system produces a countdown signal that is distributed to mission control system devices. The stability of the countdown signal is essential for the main launch-related devices because they perform reserved functions based on the countdown time information received from the countdown time-generating system. Therefore, a reliable and fault-tolerant design is required for the countdown time-generating system. To ensure system reliability, component devices should be redundant and faults should be monitored in real time to manage the device changeover from Active mode to Standby mode upon fault detection. In addition, designing different methods for mode changeover based on fault classification is necessary for appropriate changeover. This study presents a real-time fault monitoring and changeover system, which is based on the dual system design of countdown time-generating devices, as well as experiment on real-time fault monitoring and changeover based on fault inputs.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 추계학술대회 논문집 전력기술부문
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• pp.141-144
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• 2002

This paper describes the correction of the protective relay equipped in the dedicated line used for connecting distributed generators (DG) to power grid. The fault current measured in a relaying point might be changed according to the fault conditions. Generally, the fault current of the line to line fault or the line to ground fault at the dedicated line is much higher than the protective set value due to the large fault level. However. when the high impedance fault is occurred in the dedicated line, we may not detect it because its fault level can be lower than the generating capacity of DG. And, the protective relay with conventional set value may generate a trip signal for insertion of DG due to the large transient characteristics of generators. Through the various simulations such as the fault in the dedicated line and the insertion of DG, we show that it would be necessary to modify the protective relay set value for detecting the high impedance fault occurred in the dedicated line and for preventing the mis-operation of protective relay caused by the insertion of DG.

• 대한전기학회논문지:전력기술부문A
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• 제48권8호
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• pp.924-931
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• 1999

Most conventional protection relays are based on processing information in the spectrum that is close to or at power frequency. It is, however, widely known that faults on transmission lines produce frequency components of a wide range. High frequency signals caused by sudden changes in system voltage that occurs in the immediate post-fault period are generally outside the bandwidth of receptibility of most protection scheme. In this respect, a specially designed stack tuner is connected to the coupling capacitor of CVT, in order to capture the high frequency signals. Digital signal processing is then applied to the captured information to determine whether the fault is inside or outside the protected zone, and to discriminate the fault type. In this paper, modal transform is not applied to fault generated signals, because signals which are converted by modal transform are not have an information of each phase any longer. Instead, using peak voltage value of data windows is able to discriminate fault type. The paper concludes by presenting fault detection and discrimination of various faults on transmission line which are based on extensive simulation studies carried out on a typical 154kV Korean transmission line, using the EMTP software.

• 조명전기설비학회논문지
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• 제30권1호
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• pp.28-37
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• 2016

Fault locating is an important element to minimize the damage of power system. The computation error of fault locator may occur by the influence of the DC offset component during phasor extraction. In order to minimize the bad effects of DC offset component, this paper presents an improved fault location algorithm based on a DC offset removal filter for short fault in a double circuit transmission line. We have modeled a 154kV double circuit transmission line by the ATP software to demonstrate the effectiveness of the proposed fault locating algorithm. The line to line short faults were simulated and then collected simulation data was used. It can be seen that the error rate of fault locating estimation by the proposed algorithm decreases than the error rate of fault locating estimation by conventional algorithm.

• 설비공학논문집
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• 제18권10호
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• pp.791-799
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• 2006

The fault diagnosis technologies may be applied in order to decrease the energy consumption and the maintenance cost of an air-conditioning system. In this paper, a fault diagnosis algorithm was developed by using a neural no-fault model and a dual fuzzy logic. Five different faults, such as the compressor valve leakage, the liquid line blockage, the condenser fouling, the evaporator fouling, and the refrigerant leakage of an air-conditioning system, were considered. The fault diagnosis algorithm was tested by using a fault simulation facility. Test results showed that the algorithm developed for this study was effective to detect and diagnose various faults. Therefore, this algorithm may be practically used for the fault diagnosis of an air-conditioning system.

• 한국시뮬레이션학회논문지
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• 제20권3호
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• pp.59-67
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• 2011

본 논문에서는 오류 검출을 위해 소프트웨어 오류 추정 기법을 활용하여 항공무장 시스템인 공대지 사격의 오류 요인을 분석하기 위한 모델을 제시하고 모델을 기반으로 오류 요인 영향을 분석하였다. 선행 연구에서는 공대지 무기체계의 정확도에 영향을 미치는 오류 요소를 분석하고 결함위치추정 기법인 FBEL(Factor-based Error Localization) 기법을 제안하였으며 실사격 자료에 적용하여 오류 요소를 분석하였다. 그러나 다양한 요인 중 하나의 요인인 정확도를 고정하여 적용하므로 다양한 사격 정확도 변화에 따른 사격 오류 발생 요소와의 상관관계는 밝히지 못하였다. 본 연구에서는 사격 오류 요소의 상관관계 분석을 통하여 보다 세밀한 오류 분석 모델을 제시하고 시간과 비용이 제한적이거나 테스트 케이스가 적은 상태에서 오류 발생 가능 요소를 추정하는 방법을 제안한다. 제안된 방법은 실사격 자료를 이용한 시뮬레이션을 통해 그 효용성을 입증하였으며, 무기체계 공대지 시험평가에서 어떤 요소들이 정확도에 영향을 미치는 지를 분석하는데 성공적으로 활용될 수 있음을 보였다.

• 설비공학논문집
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• 제20권7호
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• pp.508-516
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• 2008

Fault detection and diagnosis(FDD) system is beneficial in equipment management by providing the operator with tools which can help find out a failure of the system. An experimental study has been performed on fault detection and diagnosis method for a water chiller. Bayes classifier, which is one of classical pattern classifiers, is adopted in deciding whether fault occurred or not. Failure modes in this study include refrigerant leakage, decrease in mass flow rate of the chilled water and cooling water, and sensor error of the cooling water inlet temperature. It is possible to detect and diagnose faults in this study by adopting FDD algorithm using only four parameters(compressor outlet temperature, chilled water inlet temperature, cooling water outlet temperature and compressor power consumption). Refrigerant leakage failure is detected at 20% of refrigerant leakage. When mass flow rate of the chilled and cooling water decrease more than 8% or 12%, FDD algorithm can detect the faults. The deviation of temperature sensor over $0.6^{\circ}C$ can be detected as fault.

• Geomechanics and Engineering
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• 제14권4호
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• pp.337-344
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• 2018

The study of the mining effect influenced by a normal fault has great significance concerning the prediction and prevention of fault rock burst. According to the occurrence condition of a normal fault, the stress evolution of the working face and fault plane, the movement characteristics of overlying strata, and the law of fault slipping when the working face advances from footwall to hanging wall are studied utilizing UDEC numerical simulation. Then the inducing-mechanism of fault rock burst is revealed. Results show that in pre-mining, the in situ stress distribution of two fault walls in the fault-affected zone is notably different. When the working face mines in the footwall, the abutment stress distributes in a "double peak" pattern. The ratio of shear stress to normal stress and the fault slipping have the obvious spatial and temporal characteristics because they vary gradually from the higher layer to the lower one orderly. The variation of roof subsidence is in S-shape which includes slow deformation, violent slipping, deformation induced by the hanging wall strata rotation, and movement stability. The simulation results are verified via several engineering cases of fault rock burst. Moreover, it can provide a reference for prevention and control of rock burst in a fault-affected zone under similar conditions.