• Journal of Electrical Engineering and Technology
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• v.10 no.2
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• pp.474-486
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• 2015

This paper proposes a multi-objective optimal placement method of Phasor Measurement Units (PMUs) in large electric transmission systems. It is proposed for minimizing the number of PMUs for complete system observability and maximizing measurement redundancy of the buses, simultaneously. The measurement redundancy of the bus indicates that number of times a bus is able to monitor more than once by PMUs set. A high level of measurement redundancy can maximize the system observability and it is required for a reliable power system state estimation. Therefore, simultaneous optimizations of the two conflicting objectives are performed using a binary coded firefly algorithm. The complete observability of the power system is first prepared and then, single line loss contingency condition is added to the main model. The practical measurement limitation of PMUs is also considered. The efficiency of the proposed method is validated on IEEE 14, 30, 57 and 118 bus test systems and a real and large- scale Polish 2383 bus system. The valuable approach of firefly algorithm is demonstrated in finding the optimal number of PMUs and their locations by comparing its performance with earlier works.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.593-597
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• 1996

This paper describes a method for drawing check of dimension errors, such as deficiency and redundancy of dimensions, input-errors in dimension figures and symbols, etc. The logic for finding dimensional errors is written by using the Turbo C language. Checking for deficiency and redundancy of global dimensions has been performed applying Graph Theory. Especialy, this paper gives an account of checking method for annular parts.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.8
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• pp.1291-1298
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• 2004

In development of monitoring and control systems, one of the most important points is to consider a redundancy so that the system can be operated normally although hardware faults are partly occurred. The purpose of this paper is to introduce a monitoring and control system with a redundancy function for I/O servers and communication networks. I/O servers composed with an active server and a standby server. Each server also has 3 communication ports, 2 ports of them were connected to field units and the other 1 port was connected to the other server. Field units have to be constructed to 2 communication ports connected I/O servers through communication lines. Also, server communication module was implemented for analyzing and handling fault elements. and was submodularized for linking easily with a monitoring and control module. An experiment with 2 servers and 2 field units was constructed to demonstrate its effectiveness.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.4
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• pp.426-432
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• 2009

In this paper, redundancy resolution of UVMS (underwater vehicle-manipulate. system) is addressed. In general, UVMS has redundant DOFs (degrees of freedom) as many as DOFs of manipulator and these redundant DOFs can be used to optimize the configuration of UVMS while satisfying given tasks. We propose a performance index for redundancy resolution which minimizes the restoring moments of UVMS. The restoring moment can cause unintentional change of poses of UVMS. If the restoring moments remain small, control effort for keeping the poses of UVMS decreases. This means that energy consumption can be reduced by minimizing the restoring moments during conducting tasks. Proposed performance measure is optimized by gradient projection method. Generated trajectories by this redundancy resolution are tracked by robust PID controller. Numerical simulations are presented to demonstrate performance of the proposed algorithm.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.717-720
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• 2000

Event-driven communication protocols such as CAN(Controller Area Network) have inherent packet delays due to the contention process for the use of network medium. These delays are stochastic in nature because most packets arrive at random time instants. The stochastic property of the delay adversely influences the control system's performance in terms of stability, responsiveness and steady-state error. Another problem for safety-critical application such as brake-by-wire systems is the reliability of the communication modules that can fail abruptly. This paper deals with two methods to overcome the above problems : (i) scheduling method that can maintain packet delays under some acceptable level, and (ii) redundancy management of communication modules that prescribes dual-redundancy modules' behavior when one of them fails.

• Proceedings of the Korean Reliability Society Conference
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• 2000.11a
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• pp.399-404
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• 2000

Redundancy allocation problems have been considered at single-level systems and it may be the best policy in some specific situations, but not in general. With regards to reliability, it is most effective to allocate the lowest objects, because parallel-series systems are more reliable than series-parallel systems. However, the smaller and tower in the system an object is, the more time and accuracy are needed for duplicating it, and so, the cost can be decreased by using modular redundancy. Therefore, providing redundancy at high levels like as modules or subsystems, can be more economical than providing redundancy at low levels or duplicating components. In this paper, the problem in which redundancy is allocated at all level in a series system is addressed, a mixed integer nonlinear programming model is presented and genetic algorithm is proposed. An example illustrates the procedure.

• Journal of Advanced Technology Convergence
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• v.2 no.3
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• pp.9-15
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• 2023

Recently, various public services are being performed based on information systems as the informatization business spreads. Public administration services based on these information systems provide internal and external services. In recent years, as the construction of cloud-based public services has been expanded, the advancement of information systems has attracted attention. In particular, as the dependence on information systems increases, the establishment of a response system to prevent dangerous situations such as interruption and paralysis of information systems in advance has become a hot topic not only in companies but also in public institutions. Therefore, in this paper, a disaster recovery system was designed and built to maximize the efficiency of system operation and shorten recovery time through service conversion automation of the disaster recovery system. The integrated DR server redundancy test, web server redundancy test, FC-IP redundancy test, and SAN switch redundancy test were performed respectively by applying the disaster recovery system designed and built according to the method proposed in the paper.

• International Journal of Control, Automation, and Systems
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• v.6 no.1
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• pp.126-134
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• 2008

As many systems depend on electronics, concern for fault tolerance is growing rapidly. For example, a car with its steering controlled by electronics and no mechanical linkage from steering wheel to front tires (steer-by-wire) should be fault tolerant because a failure can come without any warning and its effect is devastating. In order to make system fault tolerant, there has been a body of research mainly from aerospace field. This paper presents the structure of predictive hybrid redundancy that can remove most erroneous values. In addition, several numerical simulation results are given where the predictive hybrid redundancy outperforms wellknown average and median voters.

• Journal of Korea Multimedia Society
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• v.25 no.6
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• pp.793-806
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• 2022

As the IMO introduced MASS (Maritime Autonomous Surface Ships), ISO(International Organization for Standardization) announced ISO 19847 of a maritime data sharing standard for collecting and remotely managing data of ship systems. Previous literature evaluated the risk using HAZOP for ISO 19847 and proved that risk assessment is useful through experiments. However, redundancy of ISO 19847 ship data server which is one of the risk reduction method suggested in previous literature, was designed but couldn't tested due to the limitations of the conditions. So, in this study, to prove the usefulness of the ship data server redundancy of ISO 19847 which was not tested in previous literature. It based on the design of previous literature, and the network of ship data servers was modeled using the SES/DEVS format and simulated using the DEVS# open source library.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.739-744
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• 2008

Human-like biped robot is a representative multi-links manipulator and undoubted redundancy system. However many researchers separate biped robot into each limb and analyze the members individually for the convenience analysis. This approach is not desirable for natural trajectory generation and energy optimization. This paper proposes the analysis method considering both legs together and the weighted pseudoinverse optimizing energy consumption.