• 한국정보과학회논문지:시스템및이론
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• 제34권2호
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• pp.65-72
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• 2007

임베디드 시스템의 신인도(Dependability)를 높이기 위해 기존 컴퓨터시스템에서 주로 사용되는 결함허용(Fault-tolerant) 기법을 그대로 적용시키는 것은 임베디드 시스템의 엄격한 비용 제약과 설치공간 부족 등을 고려할 때 적합하지 않다. 본 논문에서는 각 시스템 구성요소(Component)들의 여분(Redundancy)을 최소한도로 사용하는 임베디드 시스템에 적합한 소프트웨어 결함허용 기법을 제안한다. 이를 위하여 임베디드 시스템의 신인도를 반영하기 위한 기준인 유용도(Utility) 척도를 정의하고, 실제 시스템의 결함허용을 위해 각각의 시스템 구성요소들의 재구성(Reconfiguration) 조합에 대한 유용도 평가를 수행하였다. 이러한 유용도 평가는 일반적으로는 지수복잡성(Exponential Complexity)을 가지게 되나, 본 논문에서는 각각의 구성요소에 대한 소프트웨어 수준의 계층적 그룹화 개념을 이용하여 복잡도를 크게 감소시켰다. 이를 통해 임베디드 시스템의 일부 부품에 결함이 발생했을 시, 시스템의 고장(Failure)을 방지 할 수 있도록 전체 시스템 단계에서 가능한 최대 유용도를 제공하는 구성조합으로의 재구성 작업을 가능하게 하였다.

• 한국군사과학기술학회지
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• 제10권2호
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• pp.107-114
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• 2007

This paper describes the Petri Net(PN) model for reliability analysis of fault-tolerant dual Ethernet which Is applied in Naval Combat System. The network for Naval Combat System performs failure detection and auto path recovery by handling redundant path in case of temporary link failure. After studying the behavior of this kind of network, the reliability analysis model is proposed using stochastic Petri Net and continuous-time Markov chains. Finally, the numerical result is analyzed according to changing the failure rate and the recover rate of link.

• 한국산학기술학회논문지
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• 제11권1호
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• pp.182-189
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• 2010

본 논문에서는 비동기적 분산시스템에서 고장 추적 장치를 이용한 상호배제의 문제를 서술하고 이러한 문제를 해결하는 가장 약한 고장 추적 장치를 결정하고자 한다. 이를 위해서 $M^*$라고 정의한 modal failure detector star 고장 추적 장치를 정의하고 $M^*$를 이용해서 상호배제 문제는 비동기적 분산 시스템에서 해결 가능함을 보인다. $M^*$는 perfect failure detector P보다 확실히 약하며 eventually perfect failure detector ◇P보다는 강한 고장추적 장치이다. 본 논문에서는 어떤 환경 안에서 이러한 문제가 해결 가능함을 보인다.

• 한국산업융합학회 논문집
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• 제25권6_2호
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• pp.1003-1008
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• 2022

This paper proposes a method related to fault tolerance operation and characteristic analysis of asymmetric 6-phase permanent magnet synchronous motor. In general, motor drive systems with multi-phase structures can be continuously operated despite a reduction of power and speed by using a phase changeover or control techniques according to the failures. As a result, it is widely used in industrial fields such as aviation and defense, which require high efficiency and high reliability. In this paper, the second order ripple of the electrical fundamental freuqnecy occurs in the dq-axis currents of the synchronous coordinate system through mathematical analysis according to the switch open of the dual 3-phase inverter. Therefore, the fault tolerant operation method is presented by applying the fault detection method with a constant cycle for continuous operations. The effectiveness of the proposed fault tolerance operation method is verified through the several experiments.

• 한국통신학회논문지
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• 제21권8호
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• pp.1989-2002
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• 1996

In this paper, we describe several warm standby fault-tolerant models and their operation methods applicable to telephone switching control systems which have dual module structure and need high availability. Unavailabilities of the system implemented by four different methods for each model are computed by using the Markov state model, and then are compared for system performance evaluation. As the results ofsimulations, the warm standby model with triple processors is best in the aspect of data loss, while in most cases the warm standby model with doble processors based on no standby check method provides the highest system avaiability. Periodic changeover increases the system unavailability, but the preriodic standby check on standby module decreases the system unavailability of warm standby model with a single processor and with double processors. On the other hands, the variationas of warm standby model with a single processor and with double processors. On the other hand, the variations of data recovery time and personnel recovery rate have little effect on the system unavailtability.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 A
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• pp.355-358
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• 1998

Train control and monitoring system for the railway train requires a reliable real-time communication network. The system have various functions, diagnostics, passenger informations, and fault-tolerant controls. For this system, an international standard called TCN(Train Communication Network) is proposed by IEC and the train industries. The TCN is composed of two layers, wire train bus(WTB) and multifunction vehicle bus(MVB). This paper evaluates the performance of the proposed WTB and modified WTB. And computer simulations are performed. The evaluated results can be used for the fault tolerant network in the railway train system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권1호
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• pp.35-57
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• 2021

Fog computing aims to provide the solution of bandwidth, network latency and energy consumption problems of cloud computing. Likewise, management of data generated by healthcare IoT devices is one of the significant applications of fog computing. Huge amount of data is being generated by healthcare IoT devices and such types of data is required to be managed efficiently, with low latency, without failure, and with minimum energy consumption and low cost. Failures of task or node can cause more latency, maximum energy consumption and high cost. Thus, a failure free, cost efficient, and energy aware management and scheduling scheme for data generated by healthcare IoT devices not only improves the performance of the system but also saves the precious lives of patients because of due to minimum latency and provision of fault tolerance. Therefore, to address all such challenges with regard to data management and fault tolerance, we have presented a Fault Tolerant Data management (FTDM) scheme for healthcare IoT in fog computing. In FTDM, the data generated by healthcare IoT devices is efficiently organized and managed through well-defined components and steps. A two way fault-tolerant mechanism i.e., task-based fault-tolerance and node-based fault-tolerance, is provided in FTDM through which failure of tasks and nodes are managed. The paper considers energy consumption, execution cost, network usage, latency, and execution time as performance evaluation parameters. The simulation results show significantly improvements which are performed using iFogSim. Further, the simulation results show that the proposed FTDM strategy reduces energy consumption 3.97%, execution cost 5.09%, network usage 25.88%, latency 44.15% and execution time 48.89% as compared with existing Greedy Knapsack Scheduling (GKS) strategy. Moreover, it is worthwhile to mention that sometimes the patients are required to be treated remotely due to non-availability of facilities or due to some infectious diseases such as COVID-19. Thus, in such circumstances, the proposed strategy is significantly efficient.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.2335-2339
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• 2003

To prevent the critical situation due to the fault in the aircraft sensor system, the fault tolerant system with triple or quadruple redundancy can be made. However, if the faults are occurred in two or more than sensors simultaneously, the conventional fault detection process, such as cross-channel monitoring, may give the wrong fault alarm. For this case, we can detect the fault by estimating the state vector based on the system dynamics model, which is nonlinear for aircraft. In this paper, we propose the unscented Kalman filter to estimate the nonlinear state vector. This filter utilizes the so-called unscented transformation of sigma points featured the statistical characteristics of the random variable. For verification, we perform the simulations for F-16 aircraft with accelerometers, gyros, GPS and air data system.

• 한국통신학회논문지
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• 제17권11호
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• pp.1279-1289
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• 1992

고장 방지 시스템은 하드웨어나 소프트웨어의 여분 (Redundancy)을 이용하여 신뢰도(Reliability) 및 안전도(Safety)를 향상 시킨다. 시스템의 대상 영역(application areas)에 따라 고장 마스크(fault mask), 고장검출(fault detection), 고장 확인(fault identification)등의 기법을 선택하여 이용한다. 본 연구에서는 최소의 하드웨어와 소프트웨어의 여분을 이용하는 DMR(Double Modular Redundancy) 시스템을 대기 모듈(standby module)과 Fail-safe 모듈로 동작 시킬때 신뢰도와 안전도의 특성을 비교 제시한다. 또한 자기 진단 프로그램의 과도 오류 방지 능력에 대한 시스템의 MTTF를 비교함으로서 과도 오류를 취급하는 효과적인 방법을 제시하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.1414-1419
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• 2011

In this paper we study the modeling to quantitatively assess the failure rate of USN system designed for fault-tolerant architecture, aiming at applying the world's best domestic USN technology to safety-critical railways. In order to apply the USN system to the safety-critical field like a train control sector that the failures of controllers may cause severe railway accidents such as train collision and derailment, the quantitative reliability and safety evaluation recommended in IEC 62278 must be preceded. We also develop the evaluation model for overall system failure rate for the distributed network structure, which is the characteristics of USN system. Especially, we allocate reliability targets to component units, and present an availability evaluation plan through the plan on the quantitative achievement of failure rate for sensor nodes, gateways, radio-communication network and servers, along with the failure rate model of the overall system considering network operational features.