• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 D
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• pp.2197-2199
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• 2003

Most of distributed PLC system is secured reliability of the system by fully duplicated controller. But it costs too much. In this paper, we proposed fault tolerant control using minimum spare controllers. First, the system is modeled using Galois field. Next, we designed additional spare controllers using the parity code of two dimensions. Finally, the algorithm for producing estimated output in remote I/O when the fault occurs was suggested. This method will be applied to an automatic system in order to increase reliability and improve cost performance.

• 전력전자학회논문지
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• 제16권4호
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• pp.351-357
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• 2011

영구자석 동기발전기의 벡터제어를 위해서는 회전자 위치가 필요하며 엔코더와 같은 위치센서가 위치 검출 목적으로 일반적으로 사용되고 있다. 그러나 위치센서의 사용은 영구자석 동기전동기 제어시스템의 신뢰성을 저하시킨다. 본 논문에서는 영구자석 동기전동기 제어시스템을 위한 위치센서 고장 회피 제어 방법을 제안한다. 확장 유기전력에 기반한 센서리스 위치 추정 알고리즘을 센서를 이용하는 벡터 제어와 병렬로 수행함으로써 위치센서 고장발생 시점에서 센서리스 벡터제어로 신속히 재구성할 수 있도록 하였다. 실험을 통해 제안된 방식의 유용성을 보인다.

• 대한기계학회논문집A
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• 제37권6호
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• pp.731-738
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• 2013

본 논문은 6 륜 독립구동/독립조향 차량의 독립 스티어-바이-와이어 장치의 고장 안전 주행 제어방법을 제시하였다. 조향부 고장 휠의 횡방향 타이어 힘이 차량 선회 운동에 저항력으로 작용할 수 있으므로, 이를 줄이기 위하여 본 고장 안전 주행 제어 알고리즘은 조향부 고장 휠에 높은 슬립률이 발생하도록 토크 입력을 가한다. 고슬립으로 인한 조향부 고장 휠의 종방향 타이어 힘 증가를 고려하기 위하여 종방향 타이어 힘을 추정하여 고장나지 않은 휠의 구동력 최적 분배에 구속 조건에 포함시킨다. 개루프 조향 및 폐루프 조향 시뮬레이션 결과 조향부 고장이 발생한 차량의 주행시 고장을 고려하지 않은 최적 구동력 분배 제어에 비하여 본 알고리즘 적용시 차량의 주행 성능이 보정됨을 확인하였다.

• International Journal of Aeronautical and Space Sciences
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• 제11권2호
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• pp.80-86
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• 2010

We propose a spacecraft attitude estimation algorithm using a federated unscented Kalman filter. For nonlinear spacecraft systems, the unscented Kalman filter provides better performance than the extended Kalman filter. Also, the decentralized scheme in the federated configuration makes a robust system because a sensor fault can be easily detected and isolated by the fault detection and isolation algorithm through a sensitivity factor. Using the proposed algorithm, the spacecraft can continuously perform a given mission despite navigation sensor faults. Numerical simulation is performed to verify the performance of the proposed attitude estimation algorithm.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1998년도 창립기념 춘계학술대회 논문집
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• pp.408-418
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• 1998

This paper presents the implementation of comparator which is self-testing with respect to the faults caused by any single physical defect likely to occur in NMOS and CMOS integrated circuit. The goal is to use it for the fault-tolerant system. First, a new fault model for PLA(Programmable Logic Array) is presented. This model reflects several physical defects in VLSI circuits. It focuses on the designs based on PLA because VLSI chips are far too complex to allow detailed analysis of all the possible physical defects that can occur and of the effects on the operation of the circuit. Second, this paper shows that these design, which has been implemented with 2 level AND-ORor NOR-NOR circuit, are optimal in term of size. And it also presents a formal proof that a comparator implemented using NOR-NOR PLA, based on these design, is sol f-testing with respect to most single faults in the presented fault model. Finally, it discusses the application of the self-testing comparator as a building block for the implementation of the fault-tolerant system.

• Journal of Power Electronics
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• 제15권3호
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• pp.796-805
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• 2015

New direct and indirect current control methods for a fault-tolerant active power filter topology are presented in this paper. Since a three-phase four-switch topology has a phase bridge current which cannot be directly controlled, a hysteresis control method in the α-β plane which controls the three-phase current in the two-phase stationary coordinate system is proposed. The improved SVPWM algorithm is able to eliminate the operation of the trigonometric functions in the traditional algorithm by rotating the α-β coordinates and alternating the sequence of the output vectors, which in turn simplifies the algorithm and reduces the switching frequency. The selection of the DC-side reference voltage and DC-side capacitor equalization strategy are also discussed. Simulation and experiments demonstrate that the proposed control method is correct and feasible.

• International Journal of Control, Automation, and Systems
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• 제5권6호
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• pp.707-711
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• 2007

An observer-based fault tolerant control (FTC) method is proposed for constrained switched systems (CSS) with input constraints. A family of Lyapunov-based bounded controllers are designed to ensure that, whenever actuator faults occur at the dwell time period of each continuous mode, the mode is always within its corresponding stability region. A set of switching laws are designed to guarantee the asymptotic stability of the overall CSS. The fixed stability regions on which the FTC method is based are also relaxed by the proposed variable stability regions. An example of CPU processing illustrates the effectiveness of proposed method.

• Journal of Power Electronics
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• 제18권1호
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• pp.56-69
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• 2018

In this paper, an improved Space Vector Modulation (SVM) based fault tolerant operation on a nine-level Cascaded H-Bridge (CHB) inverter with an additional backup circuit is proposed. Any type of fault in a power converter may result in a power interruption and productivity loss. Three different faults on H-bridge modules in all three phases based on the SVM approach are investigated with diagrams. Any fault in an inverter phase creates an unbalanced output voltage, which can lead to instability in the system. An additional auxiliary unit is connected in series to the three phase cascaded H-bridge circuit. With the help of this and the redundant switching states in SVM, the CHB inverter produces a balanced output with low harmonic distortion. This ensures high DC bus utilization under numerous fault conditions in three phases, which improves the system reliability. Simulation results are presented on three phase nine-level inverter with the automatic fault detection algorithm in the MATLAB/SIMULINK software tool, and experimental results are presented with DSP on five-level inverter to validate the practicality of the proposed SVM fault tolerance strategy on a CHB inverter with an auxiliary circuit.

• 센서학회지
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• 제16권1호
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• pp.52-61
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• 2007

Networked embedded systems using the smart device and fieldbus technologies are now found in many industrial fields including process automation and automobiles. However the discrepancy between a node's view of current time and the rest of the system can cause many difficulties in the design and implementation of a networked system. To provide a networked system with a global reference time, the problem of clock synchronization has been intensively studied over the decades. However, many of the existing solutions, which are mainly developed for large scale distributed computer systems, cannot be directly applied to embedded systems. This paper presents a fault-tolerant clock synchronization technique that can be used for a low-cost embedded system using a CAN bus. The effectiveness of the proposed method is demonstrated with a set of microcontrollers and DC motor-based actuators.

• 한국자동차공학회논문집
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• 제12권1호
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• pp.216-221
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• 2004

This paper describes a fault detection and fault handling algorithm to be used in a longitudinal vehicle cruise control systems. The fault diagnosis system consists of two structures to generate proper residuals and to find that which component has a fault. A systematic design of the fault diagnosis system using model-based techniques is presented. A linear observer is used to create a set of signals sensitive to faults in a radar sensor. The fault handling system consists of two structures to compensate for faults and degraded system performance. Simulation results show that the algorithm is effective for a fault diagnosis and handling in a longitudinal vehicle cruise control system.