• 한국정보전자통신기술학회논문지
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• 제9권3호
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• pp.306-311
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• 2016

소프트웨어 개발과정에서 소프트웨어 신뢰성은 매우 중요한 이슈이다. 소프트웨어 고장분석을 위한 유한고장 비동질적인 포아송과정에서 고장발생률이 상수이거나, 단조 증가 또는 단조 감소하는 패턴을 가질 수 있다. 본 연구에서는 소프트웨어 제품 테스팅 과정에서 관측고장시간에 근거한 로그 및 지수형 결함 발생률을 고려한 소프트웨어 신뢰성 모형에 대하여 연구 하였다. 신뢰성 분야에서 많이 사용되는 Goel-Okumoto모형을 이용한 새로운 로그 및 지수형 결함 확률을 반영한 문제를 제시하였다. 수명분포는 유한고장 비동질적인 포아송과정을 이용하고 모수추정법은 최우 추정법을 이용 하였다. 따라서 본 논문에서는 로그 및 지수형 결함발생률을 고려한 소프트웨어 모형분석을 위하여 소프트웨어 고장 시간간격 자료를 적용하여 비교 분석하였다. 본 연구에서 제안된 방법은 로그 및 지수형 결함발생률을 고려한모형도 신뢰성 측면에서 효율적이기 때문에 (결정계수가 80% 이상) 이 분야에서 기존 모형의 하나의 대안으로 사용할 수 있음을 확인 할 수 있었다. 이 연구를 통하여 소프트웨어 개발자들은 다양한 수명분포를 고려함으로서 소프트웨어 고장형태에 대한 사전지식을 파악하는데 도움을 줄 수 있으리라 사료 된다.

• 전기학회논문지
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• 제63권3호
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• pp.376-382
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• 2014

E-Actuator is an essential part of an eVGT, it receives the command from the main ECU and controls the vane. An e-Actuator failure can cause an abrupt change in engine output and it may induce an accident. Therefore, it is required to detect anomalies in the e-Actuator in real time to prevent accidents. In this paper, an e-Actuator fault detection method using on-line parameter identification is proposed. To implement on-line fault detection algorithm, many constraints are considered. The test input and sampling rate are selected considering the constraints. And new recursive system identification algorithm is proposed which reduces the memory and MCU power dramatically. The relationship between the identified parameters and real elements such as gears, spring and motor are derived. The fault detection method using the relationship is proposed. The experiments with the real broken gears show the effectiveness of the proposed algorithm. It is expected that the real time fault detection is possible and it can improve the safety of eVGT system.

• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2485-2492
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• 2018

The rapid development of large-scale integrated circuits has brought great challenges to the circuit testing and diagnosis, and due to the lack of exact fault models, inaccurate analog components tolerance, and some nonlinear factors, the analog circuit fault diagnosis is still regarded as an extremely difficult problem. To cope with the problem that it's difficult to extract fault features effectively from masses of original data of the nonlinear continuous analog circuit output signal, a novel approach of feature extraction and dimension reduction for analog circuit fault diagnosis based on wavelet packet decomposition, local linear embedding algorithm, and clone selection algorithm (WPD-LLE-CSA) is proposed. The proposed method can identify faulty components in complicated analog circuits with a high accuracy above 99%. Compared with the existing feature extraction methods, the proposed method can significantly reduce the quantity of features with less time spent under the premise of maintaining a high level of diagnosing rate, and also the ratio of dimensionality reduction was discussed. Several groups of experiments are conducted to demonstrate the efficiency of the proposed method.

• 정보보호학회논문지
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• 제23권3호
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• pp.371-381
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• 2013

정보보호 장치를 이용하여 데이터의 기밀성을 제공할 경우, 내부에 저장된 비밀 키를 사용하여 암호화를 수행한다. 그러나 최근 공격자가 암호화 연산 시에 오류를 주입하는 방법을 사용하여 내부의 비밀 키를 찾아낼 수 있는 오류 주입 공격 방법들이 제시되었다. 특히, 오류 주입 공격으로 블록 암호 ARIA를 공격할 경우 약 33개 정도의 오류 암호문만 있으면 비밀 키를 공격할 수 있다. 본 논문에서는 ARIA 암호 시스템에서 입 출력 정보들간의 차분 상태를 검사하는 방법으로 오류 주입 공격을 방어하는 오류 주입 탐지 방안을 제안한다. 제안 방법은 오류 탐지 능력이 우수할 뿐 아니라 연산 오버헤드가 적어 매우 효율적임을 시뮬레이션을 통해 확인하였다.

• 한국초전도ㆍ저온공학회논문지
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• 제6권2호
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• pp.25-28
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• 2004

Three-phase inductive superconducting fault current limiter (SFCL) with DC reactor rated on 6.6 $KV_{rms}/200 A_{rms}$ has been developed in Korea. This system consists of one DC reactor, AC/DC power converter, and a three-phase transformer, which is called magnetic core reactor (MCR). This paper deals with the short-circuit analysis of the SFCL. The DC reactor was the HTS solenoid coil whose inductance was 84mH. The power converter was performed as the dual-mode operation for dividing voltage between the rectifying devices. The short-term normal operation (1 see) and short-circuit tests (2∼3 cycles) of this SFCL were performed successfully. In regular short-circuit test, the fault current was limited as 30% of rated short-circuit current at 2 cycles after the fault. The experimental results have a very similar tendency to the simulation results. Using the technique for the fault detection and SCR firing control, the fault current limiting rate of the SFCL was improved. From this research, the parameters for design and manufacture of large-scale SFCL were obtained.

• 한국멀티미디어학회논문지
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• 제20권11호
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• pp.1811-1819
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• 2017

As the induction motor is the core production equipment of the industry, it is necessary to construct a fault prediction and diagnosis system through continuous monitoring. Many researches have been conducted on motor fault diagnosis algorithm based on signal processing techniques using Fourier transform, neural networks, and fuzzy inference techniques. In this paper, we propose a fault diagnosis method of induction motor using LPC and DNN. To evaluate the performance of the proposed method, the fault diagnosis was carried out using the vibration data of the induction motor in steady state and simulated various fault conditions. Experimental results show that the learning time of our proposed method and the conventional spectrum+DNN method is 139 seconds and 974 seconds each executed on the experimental PC, and our method reduces execution time by 1/8 compared with conventional method. And the success rate of the proposed method is 98.08%, which is similar to 99.54% of the conventional method.

• 한국소음진동공학회논문집
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• 제16권1호
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• pp.27-33
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• 2006

Fault diagnosis and condition monitoring for rotating machines are important for efficiency and accident prevention. The process of fault diagnosis is to extract the feature of signals and to classify each state. Conventionally, fault diagnosis has been developed by combining signal processing techniques for spectral analysis and pattern recognition, however these methods are not able to diagnose correctly for certain rotating machines and some faulty phenomena. In this paper, we add a minimum detection error algorithm to the previous method to reduce detection error rate. Vibration signals of the induction motor are measured and divided into subband signals. Each subband signal is processed to obtain the RMS, standard deviation and the statistic data for constructing the feature extraction vectors. We make a study of the fault diagnosis system that the feature extraction vectors are applied to K-means clustering algorithm and minimum detection error algorithm.

• 터널과지하공간
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• 제29권3호
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• pp.197-213
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• 2019

본 연구에서는 TOUGH-FLAC 연동해석기법을 이용하여 Mont Terri 지하연구시설에서 수행된 단층 내 물 주입시험을 수치적으로 모델링하고, 단층의 재활성과 수리역학적 거동 특성을 살펴보았다. TOUGH2 해석에서는 단층을 Darcy의 법칙과 삼승법칙(Cubic law)을 따르는 연속체 요소로 모델링하였으며, FLAC3D 해석에서는 미끄러짐과 개폐가 허용되는 불연속 인터페이스 요소를 통해 모사하였다. 현장에서 획득한 단층의 균열개방압력(fracture opening pressure), 주입율, 모니터링 압력, 변위 곡선 등을 바탕으로, 단층의 탄성적 변형과 파괴에 의한 수직팽창 특성을 반영할 수 있는 수리간극모델과 수리역학 커플링 관계를 해석모델에 반영하였다. 한편, 현지응력 조건, 단층의 강도 및 변형 특성에 따른 파라미터 해석을 실시하여 각 입력변수가 해석 결과에 미치는 영향을 분석하였으며, 이를 통해 현장시험 결과를 가장 잘 재현할 수 있는 파라미터 조합을 선정하였다. 해석 결과, 균열개방압력에서 단층의 주입율과 모니터링 압력이 크게 증가하는 현상을 합리적으로 재현할 수 있었다. 하지만, 동일한 입력 변수 조건에서 단층의 전단변위와 파괴영역의 범위는 현장시험 결과에 비해 과대평가되는 결과를 보였다. 이는 해석모델에서는 고압의 주입조건에서 단층의 지속적인 전단파괴가 유도되는 반면, 현장에서는 수리간극의 변화가 전단 미끄러짐보다는 인장력에 의한 단층면의 개방(tensile opening)에 크게 의존하는 것으로 추정되기 때문이다.

• 제어로봇시스템학회논문지
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• 제14권1호
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• pp.49-53
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• 2008

A fuzzy inference logic system is proposed for gas turbine engine fault isolation. The gas path measurements used for fault isolation are exhaust gas temperature, low and high rotor speed, and fuel flow. The fuzzy inference logic uses rules developed from a model of performance influence coefficients to isolate engine faults while accounting for uncertainty in gas path measurements. Inputs to the fuzzy inference logic system are measurement deviations of gas path parameters which are transferred directly from the ECM(Engine Control Monitoring) program and outputs are engine module faults. The proposed fuzzy inference logic system is tested using simulated data developed from the ECM trend plot reports and the results show that the proposed fuzzy inference logic system isolates module faults with high accuracy rate in the environment of high level of uncertainty.

• 한국초전도ㆍ저온공학회논문지
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• 제15권4호
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• pp.34-38
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• 2013

According to the increase of electric consumption nowadays, power system becomes complicated. Due to this, the size of single line-to-ground fault from power system also increases to have many problems. In order to resolve these problems effectively, an Superconducting Fault Current Limiter(SFCL) was proposed and continuous study has been done. In this paper, an SFCL was combined to the neutral line of a transformer. An superconductivity has the characteristics of zero resistance below critical temperature. because of this, SFCL has nearly zero resistance. so we connecting SFCL to neutral line will not only have any loss in the normal operation but also have the less burden of electric power because of only limiting the initial fault current. We analyzed the characteristics of current, voltage according to the changes of turn ratio of 3 phase system in case of combinations of an SFCL to the neutral line. It was confirmed that the limiting rate of initial fault current by the increase of turn ratio was reduced.