• Journal of Advanced Navigation Technology
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• v.21 no.5
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• pp.491-500
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• 2017

This paper investigates a low cost dual modular redundancy system based on heartbeat which can be applied to traffic control signal system. Failure of the traffic control signal system can cause traffic confusion and traffic accidents. Therefore safety and reliability of traffic control should be secured using fault tolerance technology. To do this, we configured a redundant board using the open source hardware and the heartbeat technique of Linux HA. The function of the traffic signal control system was verified and the fault recovery time was measured using fault injection test. As a result of the test, the fault recovery time was confirmed to be less than 9 seconds on average, confirming that the reliability target time is satisfied. Based on the results of this study, it is expected that it can be applied to fields requiring high reliability systems such as aviation, space, and nuclear power embedded systems.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.7
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• pp.103-109
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• 2016

Corrective control for asynchronous sequential machines is a novel automatic control theory that compensates illegal behavior or adverse effects of faults in the operation of existent asynchronous machines. In this paper, we propose a scheme of diagnosing and tolerating faults occurring to input channels of corrective control systems. The corrective controller can detect faults occurring in the input channel to the controlled machine, whereas those faults happening in the external input channel cannot be detected. The proposed scheme involves an outer operator which, upon receiving the state feedback, diagnoses a fault and sends an appropriate command signal to the controller for tolerating faults in the external input channel.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.2 no.2
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• pp.81-89
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• 2001

Space systems are operating in a changing and uncertain space environment and are desired to have autonomous capability for long periods of time without frequent telecommunications from the ground station At the same time. requirements for new set of projects/systems calling for ""autonomous"" operations for long unattended periods of time are emerging. Since, by the nature of space systems, it is desired that they perform their mission flawlessly and also it is of extreme importance to have fault-tolerant sensor/actuator sub-systems for the purpose of validating science measurement data for the mission success. Technology innovations attendant on autonomous data validation and health monitoring are articulated for a growing class of autonomous operations of space systems. The greatest need is on focus research effort to the development of a new class of fault-tolerant space systems such as attitude actuators and sensors as well as validation of measurement data from scientific instruments. The characterization for the next step in evolving the existing control processes to an autonomous posture is to embed intelligence into actively control. modify parameters and select sensor/actuator subsystems based on statistical parameters of the measurement errors in real-time. This research focuses on the identification/demonstration of critical technology innovations that will be applied to Autonomous Spacecraft Health Monitoring/Data Validation Control Systems (ASHMDVCS). Systems (ASHMDVCS).

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.88-88
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• 2000

As more and more critical commercial applications move on the Internet, providing highly available servers becomes increasingly important. One of the advantages of a clustered system is that it has hardware and software redundancy. High availability can be provided by detecting node or daemon failure and reconfiguring the system appropriately so that the workload can be taken over bi the remaining nodes in the cluster. This paper presents how to provide the guaranteeing high availability of clustering web server. The load balancer becomes a single failure point of the whole system. In order to prevent the failure of the load balancer, we setup a backup server using heartbeat, fake, mon, and checkpointing fault-tolerance method. For high availability of file servers in the cluster, we setup coda file system. Coda is a advanced network fault-tolerance distributed file system.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.572-578
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• 2008

As the railway transportation is getting faster and its operation speed has increased rapidly, its signal control has been complicated. For real time signal processing it is very important to prohibit any critical error from causing the system to malfunction. Therefore, handling complicated signals effectively while maintaining fault-tolerance capability is highly expected in modern railway transportation industry. In this paper, we suggest an SoC (Sytem-on-Chip) design method to integrate these complicated signal controlling mechanism with fault tolerant capability in a single chip. We propose an SoC solution which contains a high performance 32-bit embedded processor, digital filters and a PWM unit inside a single chip to implement ATO's, ATC's, ATP's and ATS's digital signal-processing units. We achieve an enhanced reliability against the calculation error by adding fault tolerance features to ensure the stability of each module.

• Convergence Security Journal
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• v.20 no.3
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• pp.71-78
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• 2020

Bitcoin-based blockchain technology provides an infrastructure that enables anonymous smart contracts, low-cost remittances, and online payments. However, the block-chain technology that implements the bitcoin has scalability constraints in tradeoffs between throughput and latency. To solve these problems, the Byzantine fault tolerant block-chain technique has been proposed. This technique improves throughput without increasing latency by selecting a leader and constructing many microblocks that do not contain proofs of work within the existing block by the leader. However, this technique may be less secure than existing techniques in selecting the reader.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.6
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• pp.595-601
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• 2009

A flight control system for high reliability consists of complicated redundant structures. This redundancy can improve fault tolerant characteristics of system. So, a system manager is able to choose a suitable structure using analyzed quantitative data of various redundant structures. In this paper, we analyzed redundant characteristics and reliability. We defined necessary mathematical model for analysis tool. Then we compose a reliability block diagram analysis tool applying such defined analysis model using Simulink blocks. Finally we verified the analysis tool using a commercial tool.

• Journal of the Optical Society of Korea
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• v.13 no.1
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• pp.98-106
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• 2009

This paper proposes an optical wireless transfer agent method which realizes the continuous and swift data transfer of optical wireless terminals in optical wireless networks. The unguided wireless channel generally shows frequent link disconnections and propagation delays due to weak wireless links. Specially speaking, optical wireless channels have more vulnerable links and roaming propagation delays relative to the weakness of the previous RF channels due to their low signal connectivity and small geographic coverage. Conventional optical wireless network protocols did not consider any fault models about physical link faults. Consequently, they have shown data transfer inefficiency for both data link control and physical wireless link control. To overcome these optical wireless environmental problems, this paper suggests a new wireless access point (or base station) agent system, which provides wireless or mobile clients with previous link layer protocols compensated.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.2
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• pp.304-310
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• 2016

This paper proposes a fault diagnosis method for an open-fault in inverter driving five-phase induction motor. The five-phase induction motor has a high output torque and small torque ripple in comparison to three-phase. The best advantage of the five-phase induction motor is fault diagnosis and tolerant control using redundancy of phases. This paper uses an inverter as a power converter for driving a five-phase induction motor. If a switch of inverter occurs to the open-fault, this problem is the influence on the output current and output torque. To solve this problem, there is need of an accurate diagnosis and fault switch distinction. Therefore, this paper propose a fault detection method of the open-fault switches for the fault diagnosis. First, analyzing the pattern for the open-circuit fault of one phase. next, analyzing the pattern for the open-circuit fault of each inverter switches. Through the pattern analysis, It defines the scope of each of the failure switch. Thereafter, By using an algorithm that proposes to perform a fault diagnosis method. The proposed algorithm is verified from the experiment with the 1.5 kW five-phase induction motor.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.1C
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• pp.103-111
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• 2002

In RNC of IMT-2000, main control processors such as ASP, ACP and OMP are responsible for call control function, and the high reliability and real-time property should be provided for it. So, the study of real-time fault-tolerant for it is needed. In this paper, we proposes an Task based duplication method, in which Tasks in active side operated on message unit and send the updated data to standby side after operation, log in the message to standby side for recovery during take-over. This scheme decreases the dual down and the complexity of synchronization procedure, and performs the synchronization more exactly because Tasks control the synchronization of system. This paper also proposes the fault detection and the fault handing method for effective implementation of Task based duplication. This scheme focus on increasing the fault detection rate and intercepting originally that fault data is send to standby side.