• International Journal of Control, Automation, and Systems
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• 제4권1호
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• pp.105-112
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• 2006

The main function of a reactor protection system is to maintain the reactor core integrity and the reactor coolant system pressure boundary. Generally, the reactor protection system adopts the 2-out-of-m redundant architecture to assure a reliable operation. This paper describes the safety assessment of a digital reactor protection system using the fault tree analysis technique. The fault tree technique can be expressed in terms of combinations of the basic event failures such as the random hardware failures, common cause failures, operator errors, and the fault tolerance mechanisms implemented in the reactor protection system. In this paper, a prediction method of the hardware failure rate is suggested for a digital reactor protection system, and applied to the reactor protection system being developed in Korea to identify design weak points from a safety point of view.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1123-1126
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• 2005

This paper introduces the key features of NCS (Network based Control System), which is quite a new concept in the industrial automation market. Two control systems "DCS" and "PLC" have been recognized as control systems used for process and factory automation during the past decades. However, the market requires more complex functionality, such as monitoring and operation, alarm handling and notification from remote locations using the Web or e-mail. Besides enhancing functionality, interoperability between each device and system is highly required since network and engineering tools provided by many vendors do not cooperate with each others, so that lots of conversion, reconfiguration and reprogramming are required when expanding systems. NCS can meet this requirement, installing leading-edged IT technology using international standards for network and engineering environment. NCS, which is a harmony of web functionality, networkability and a reliable control function, enables information integration and responding to the market's requirements with agility and high reliability.

• Journal of Power Electronics
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• 제10권1호
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• pp.34-42
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• 2010

Reliability is an important issue in cascaded H-bridge converters (CHB converters) because they use a high number of power semiconductors. A faulty power cell in a CHB converter can potentially lead to expensive downtime and great losses on the consumer side. With a fault-tolerant control strategy, operation can continue with the undamaged cells; thus increasing the reliability of the system. In this paper, the operating principles and the control method for a CHB multilevel rectifier are introduced. The influence of various faults on the CHB converter is investigated. The method of fault diagnosis and the bypassing of failed cells are explained. A fault-tolerant protection strategy is proposed to achieve redundancy in the CHB rectifier. The redundant H-bridge concept helps to deal with device failures and to increase system reliability. Simulation results verify the performance of the proposed strategy.

• 대한전자공학회논문지
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• 제25권2호
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• pp.204-210
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• 1988

The residue number system offers the possibility of high-speed operation and error detection/correction because of the separability of arithmetic operations on each digit. A compact residue arithmetic module named the self-checking pulse-train residue arithmetic circuit is effectively employed as the basic module, and an efficient error detection/correction algorithm in which error detection is performed in each basic module and error correction is performed based on the parallelism of residue arithmetic is also employed. In this case, the error correcting circuit is imposed in series to non-redundant system. This design method has an advantage of compact hardware. Following the proposed method, a 2nd-order recursive fault-tolerant digital filter is practically implemented, and its fault-tolerant ability is proved by noise injection testing.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.870-874
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• 2004

This paper presents a three dimensional modeling and simulations of operation and running of a wheel loader using the ADAMS program. A wheel loader consists of a bucket, a boom, a crank, a front frame, a rear frame, a bucket cylinder, two boom cylinders, two steering cylinders, nine spherical joints, six universal joints, five translation joints, three inline joints, a revolute and a fixed joint. Judging from the actual degrees of freedom of the wheel loader, proper kinematic joints are selected to exclude redundant constraints in the modeling. Through the running simulation over a bump with the three dimensional modeling, the joint reaction forces are calculated.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 춘계학술대회 논문집
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• pp.139-144
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• 2003

This study was aimed to establish failure management plan of the rubber-tired AGT light rail vehicle for its safety case, which was developed according to the Korean standardized specifications for the light rail vehicle. Vehicular 9 failure modes anticipated during the system operation were considered, which are single malfunction of redundant equipment, malfunction of train radio, public address and air compressor, battery, main circuit NFB trip, on-board ATO control device malfunction, on-board ATP control device malfunction, fail of brake release, flat tire, train emergency door open.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2000년도 춘계학술대회 논문집
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• pp.352-359
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• 2000

In this paper, the method is used that each system isolates the part in which faults are occurred in case of fault occurrence since total system is designed in the type of hot standby sparing system construction and self-checking circuit in each system is attached to the memory being of the high failure rate in common communication system. Thus reliability and availability in system are improved. In this thesis, self-checking circuit was designed using 2 out of 6 code and didn't have any effect to the system operation. For the purpose of verification, each system attached with self-checking circuit was simulated through fault injection arid the continuity of each system in hot standby sparing system was tested in case that the system was switched when faults in the system were occurred.

• 제어로봇시스템학회논문지
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• 제12권9호
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• pp.861-867
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• 2006

This paper presents the robust mobile robot localization method exploiting redundant motion information acquired from three optical mice that are installed at the bottom of a mobile robot in a regular triangular form. First, we briefly introduce a low-cost optical motion sensor, HDNS-2000, and a commercial device driver development tools, WinDriver, to be used in this research. Second, we explain the basic principle of the mobile robot localization using the motion information from three optical mice, and propose the least squares based localization algorithm which is robust to the noisy measurement and partial malfunctioning of optical mice. Third, we describe the development of the experimental optical odometer using three PC optical mice and the user-friendly graphic monitoring program. Fourth, simulations and experiments are performed to demonstrate the validity of the proposed localization method and the operation of the developed optical odometer. Finally, along with the conclusion, we suggest some future work including the installation parameter calibration, the optical mouse remodelling, and the high-performance motion sensor adoption.

• 제어로봇시스템학회논문지
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• 제4권2호
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• pp.264-272
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• 1998

This paper proposes a fault detection and recovery mechanism for a fault-tolerant Mini-MAP system, and provides detailed techniques for its implementation. This paper considers the fault-tolerant Mini-MAP system which has dual layer structure from the LLC sublayer down to the physical layer to cope with the faults of those layers. For a good fault detection, a redundant and hierarchical fault supervision architecture is proposed and its implementation technique for a stable detection operation is provided. Information for the fault location is provided from data reported with a fault detection and obtained by an additional network diagnosis. The faults are recovered by the stand-by sparing method applied for a dual network composed of two equivalent networks. A network switch mechanism is proposed to achieve a reliable and stable network function. A fault-tolerant Mini-MAP system is implemented by applying the proposed fault detection and recovery mechanism.

• Journal of electromagnetic engineering and science
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• 제12권2호
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• pp.148-154
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• 2012

In this paper, we propose an algorithm to conserve resources of the common control channel in a cognitive radio network by rejecting the redundant users using cooperative spectrum sensing. The proposed scheme is investigated under the paradigm of active spectrum sensing and a sequential detection technique. The algorithm is based on the J-divergence between the hypotheses of non primary user operation and the otherwise case. We select the most significant eigenvalues, which primarily affect the global statistical test. For the case where interference is from a secondary system transmission, a match filter is first employed to remove the degradation, and then the proposed algorithm is employed to remove the cooperative sensing nodes. Numerical results are provided and compared with conventional cases in order to validate the performance of the proposed algorithm.