• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.3
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• pp.256-265
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• 2016

Software based fault tolerance techniques are designed to allow a system to tolerate software faults in the system. Fault tolerance techniques are divided into two groups : software based fault tolerance techniques and hardware based fault tolerance techniques. We need a proper design method according to characteristics of the system. In this paper, the concepts of software based fault tolerance techniques for Dual Flight Control Computer are described. For software based fault tolerance design, we classified software failure, designed a way for failure detection and the way of recovery. Eventually the effectiveness of software based fault tolerance techniques was verified through the Software Test Environment(STE).

• Electronics and Telecommunications Trends
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• v.10 no.2 s.36
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• pp.33-43
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• 1995

시스템이 고성능화 되고 그 기능이 향상됨에 따라 사용 환경에서의 높은 신뢰성 (reliability) 및 가용성 (availability)이 중요시 된다. 신뢰성과 가용성을 높이기 위해서는 시스템이 이상 상태에서도 계속 동작을 할 수 있도록 하는 고장 허용 기능이 필수적이다. 본 고에서는 고속 병렬컴퓨터 시스템 개발에서 시스템 구조에 알맞은 고장 허용 기능 구현을 위해 상용 고장 허용 기술 중심으로 이에 구현된 기능을 알아 보고, 그 중 밀 결합 시스템의 고장 복구 기법을 살펴보았다.

• 전기의세계
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• v.26 no.2
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• pp.10-13
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• 1977

컴퓨터가 다양한 목적에 이용됨에 따라 신뢰도가 높은 즉 고장허용의 전산체계의 필요성은 증가되고 있다. 임상응용의 경우 컴퓨터의 오동작은 치명적일 수 있고 또 공정제어의 경우 귀중한 자원의 막대한 손실을 초래할 수 있다. 따라서 고장허용의 전산체계에 관한 연구는 필연적이다. 역사적으로 최초의 고장허용의 전산체계는 SAGE와 같은 군사적인 응용에 시도하였다. 2절에서는 이러한 신뢰도가 높은 기계의 시험적인 결과와 실제 운영의 경험에 입각한 고장허용의 전산체계의 설계원리를 논한다. 이어서 3절에서는 현재까지 설계된 고장허용 전산체계의 구조를 기술하며 4절에서는 현재까지 범용의 컴퓨터에 사용한 고장허용기법을 소개한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.9A
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• pp.868-877
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• 2006

Sensor network applications need synchronized time to the highest degree such as object tracking, consistent state updates, duplicate detection, and temporal order delivery. In addition, reliability issues and fault tolerance in sophisticated sensor networks have become a critical area of research today. In this paper, we proposed a fault tolerant clock management scheme in sensor networks considering two cases of fault model such as network faults and clock faults. The proposed scheme restricts the propagation of synchronization error when there are clock faults of nodes such as rapid fluctuation, severe changes in drift rate, and so on. In addition, it handles topology changes. Simulation results show that the proposed method has about $1.5{\sim}2.0$ times better performance than TPSN in the presence of faults.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04a
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• pp.70-72
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• 2003

소프트웨어 분산공유메모리 시스템의 성능이 높아짐에 따라 최근에는 큰 규모의 클러스터 상에서 사용되는 경우가 많아졌다. 그러나 시스템 규모가 커지면서 고장이 발생하는 가능성도 높아졌다. 시스템의 가용성을 높이기 위하여 고장 허용 기능을 제공하는 분산공유메모리 시스템이 요구되었으며 체크포인팅과 더불어 메시지 로깅에 대한 많은 연구가 이루어져 왔다. 본 논문에서는 고속의 네트웍을 이용하여 원격 노드의 메모리에 로깅하는 방범과 복구 방법을 제안하고 구현을 통하여 성능을 보인다. 원격 로깅은 디스크 접근을 요구하지 않으므로 오버헤드가 적으며 제한적으로 다중 노드의 고장을 허용한다.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.3
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• pp.117-124
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• 2002

This paper proposes a fault-tolerant multicasting algorithm employing the region encoding scheme in multistage interconnection networks (MIN's) containing multiple faulty switching elements. After classifying all switching elements into two subsets with equal sizes in MIN, the proposed algorithm can tolerate the faulty pattern where every fault is contained in the same subset. In order to send a multicast message to its destinations detouring faults, the proposed algorithm uses the recursive scheme that recirculates it through MIN, We prove that this algorithm can route any multicast message in only two passes through the faulty MIN.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.6
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• pp.608-618
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• 2000

We consider the problem of placing resources in a distributed computing system so that certain performance requirements may be met while minimizing the number of required resource copies, irrespective of node or link failures. To meet the requirements for high performance and high availability, minimum number of resource copies should be placed in such a way that each node has at least two copies on the node or its neighbor nodes. This is called the fault-tolerant resource placement problem in this paper. The structure of a parallel or a distributed computing system is represented by a graph. The fault-tolerant placement problem is first transformed into the problem of finding the smallest fault-tolerant dominating set in a graph. The dominating set problem is known to be NP-complete. In this paper, searching for the smallest fault-tolerant dominating set is formulated as a state-space search problem, which is then solved optimally with the well-known A* algorithm. To speed up the search, we derive heuristic information by analyzing the properties of fault-tolerant dominating sets. Some experimental results on various regular and random graphs show that the search time can be reduced dramatically using the heuristic information.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1B
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• pp.74-85
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• 2009

We propose an Agent-based Fault Tolerant Object Group model based on the agent technology and FTOG model with replication mechanism for effective object management and fault recovery. We define the five kind of agents - internal processing agent, registration agent, state handling agent, user interface agent, and service agent - that extend the functions of the FTOG model. The roles of the agents in the proposed model are to reduce the remote interactions between distributed objects and provide more effective service execution. To verify the effectiveness of the proposed model, we implemented the Intelligent Home Network Simulator (IHNS) which virtually provides general home networking services. Through the simulations, it is validated that the proposed model decreases the interactions of the object components and supports the effective fault recovery, while providing more stable and reliable services.

• 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.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2756-2758
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• 2005

본 논문에서는 제어시스템의 신뢰성 향상을 위한 고장허용제어계를 실현하기 위하여, 함수관측자를 도입한 장치고장검출(IFD)기법 및 고장보상알고리즘을 제안하고, 이를 전형적인 불안정 비선형시스템인 역진자제어계에 적용하였다. 제안된 IFDS는 기존의 다중관측자기법과 동일한 구조를 가지지만 최저차 설계가 가능한 미지입력 함수관측자를 채택함으로서 알고리즘의 단순화를 가하였을 뿐 아니라 고장량의 추정 등 다양한 설계목적을 고려하여 설계될 수 있다는 특징을 가진다. 제안된 고장 검출식별 기법의 제안된 역진자제어계를 위한 제어기, 고장검출식별 및 보상알고리즘을 모두 포함한 상태에서 고장허용제어의 가능성을 검증하였다.