• KIISE Transactions on Computing Practices
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• v.21 no.1
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• pp.29-39
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• 2015

When new inertial navigation systems for an unmanned aerial vehicles are being developed and tested, construction of a fault-tolerant system is required because of various types of hazards caused by S/W and H/W faults. In this paper, a new fault-tolerant flight system that can be deployed into one or more FCCs (Flight Control Computers) is introduced, based on a partition scheme wherein each OFP (Operational Flight Program) partition uses an independent CPU and memory slot. The new fault-tolerant navigation system utilizes one or two FCCs, and executes a primary navigation OFP under development and a stable shadow OFP partition on each node. The fault-tolerant navigation system based on a single FCC can be used for UAVs with small payloads. For larger UAVs, an additional FCC with two OFP partitions can be used to provide both H/W and S/W fault-tolerance. The developed fault-tolerant navigation system significantly removes various hazards in testing new navigation S/Ws for UAVs.

• Journal of the Korean Solar Energy Society
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• v.36 no.4
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• pp.31-40
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• 2016

The demands for photovoltaic systems on a large scale have grown dramatically and require new technologies to get the high efficiency and reliable operations of power conversion systems. These needs can be realized by the cost-effective and high performance digital revolutions and faster semiconductor switching devices. However, the new power systems have been more sophisticated and their reliability becomes critical issues. In this paper, a new fault-tolerance power conversion scheme for the photovoltaic systems is proposed. The proposed fault-tolerant scheme is able to supply energy from solar panels to loads intermittently in spite of a front boost converter open failure, and its voltage and current controllers are designed to improve the transient performance by using an average model design scheme. The proposed approach is verified both by simulations. The results will enable more timely and wide usage of alternative/renewable energy systems resulting in increased energy security.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.11
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• pp.1102-1111
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• 2007

The theory for a fault-tolerant control of homopolar magnetic bearings is developed. New coil winding law is utilized such that control fluxes are isolated for an 8-pole homopolar magnetic bearing. Decoupling chokes are not required for the fault tolerant magnetic bearing since C-core fluxes are isolated. If some of the coils or power amplifiers suddenly fail, the remaining coil currents change via a distribution matrix such that the same magnetic forces are maintained before and after failure. Lagrange multiplier optimization with equality constraints is utilized to calculate the optimal distribution matrix that maximizes the load capacity of the failed bearing. Some numerical examples of distribution matrices are provided to illustrate the theory. Simulations show that very much the same dynamic responses (orbits or displacements) are maintained throughout failure events while currents and fluxes change significantly.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.4
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• pp.351-357
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• 2011

Rotor position is essentially required for vector control of permanent magnet synchronous generator(PMSG) and position sensor such as encoder are generally used for the purpose of position sensing. However, the use of position sensor degrades reliability of PMSG control system. This paper presents position sensor fault tolerant control method for PMSG control system. Sensorless position estimator based on extended electromotive force(EMF) is operated in parallel with sensored vector control to provide rapid reconfiguration capability to sensorless vector control at the moment of position sensor fault detection. Experimental results show the effectiveness of the proposed method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.9
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• pp.1802-1808
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• 2009

A fault detection observer with finite time convergence characteristics(FT_FDO) is proposed and applied to a fault detection isolation system for a dynamic control system. The FT_FDO is a kind of dual state-observer scheme that provides with the state estimates insensitive to a specified fault and the corresponding fault estimate. The state estimates are processed to get the residual that will be logically compared with other residuals to detect and isolate the fault of interest, and the fault estimate may be used for fault compensation. The FDIS employing the FT_FDOs can be considered to be a multiple observer schemes(MOS) in which FT_FDOs are parallelly driven to generate a set of residuals to be compared each other. Due to the finite time convergence characteristics of the FT_FDO, the predetermined detection delay can be considered in the design stage of FDIS so that any fault of interest can be detected and identified in that time. It evidently resolves a well known difficulty of threshold selection owing to the transient responses of the fault detection observers(FDO) employed in FDIS. An FDIS is constructed for instruments(2-sensor, 1-actuator) in an inverted pendulum control system, and simulations are performed to show the performance of the FDIS and fault tolerant control system.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.3
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• pp.266-273
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• 2012

In this paper, the new open fault detection and tolerant operation method for 3 phase PWM rectifier is proposed. When open fault occurred on the inverter switches of 3 Phase PWM rectifier, the DC link voltage ripple is increased because the input current of the faulty phase is distorted. In this case, the quality of electric power would decrease, and the life time of DC link capacitor is decreased. The open fault is detected by a simple MRAS(Model Reference Adaptive System) without additional hardware sensors, and the tolerant operation carried out by turning on the opposite switch of the faulty switch without any redundancy. By the proposed method, the faulty phase input current can be controlled, so that 3-phase input current is balanced relatively under the faulty condition and the voltage ripple of DC link output is reduced. The validity of the proposed technique is proved on the 6kW 3-phase PWM rectifier system by simulation and experiment.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.9
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• pp.627-638
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• 2022

This paper discusses the utilization of fault-tolerant technology in the industry by analyzing the status of drone failures in the unmanned vehicle industry survey conducted in 2020. Based on the survey results of the domestic unmanned vehicle industry, we identify subsystems with high fault rates and high severity when faults occur. In addition, fault simulations of the identified subsystems are conducted to analyze the effect of the fault on the vehicles. After that, the fault diagnosis and fault compensation methods studied so far are reviewed, and research cases of the methods are examined. Moreover, the ways to apply it to actual fault cases in the unmanned vehicle industry are debated. Furthermore, based on the previous discussion, the fault-tolerant system is presented, and the consideration when designing the fault-tolerant system in the industry are studied.

• Journal of IKEEE
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• v.24 no.3
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• pp.727-734
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• 2020

Fault tolerant corrective control for asynchronous sequential machines (ASMs) with transient faults is discussed in this paper. The considered ASM is vulnerable to a kind of faults whose manifestation may arise during transient transitions of the ASM, leading to transient faults occurring in non-fundamental mode. To overcome adverse effects caused by these faults, we present a novel corrective control scheme that can detect and tolerate transient faults in non-fundamental mode. The existence condition and design algorithm for an appropriate fault tolerant controller is addressed in the framework of corrective control theory. The applicability of the proposed control methodology is demonstrated in the FPGA experiment.

• Journal of KSNVE
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• v.8 no.6
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• pp.1181-1192
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• 1998

This paper describes the performance of a full-authority neural network-based fault tolerant system within a flight control system. This fault tolerant flight control system integrates sensor and actuator failure detection, identification, and accommodation (SFDIA and AFDIA), The first task is achieved by incorporating a main neural network (MNN) and a set of n decentralized neural networks (DNNs) to create a system for achieving fault tolerant capabilities for a system with n sensors assumed to be without physical redundancy The second scheme implements the same main neural network integrated with three neural network controllers (NNCs). The function of NNCs is to regain equilibrium and to compensate for the pitching, rolling. and yawing moments induced by the failure. Particular emphasis is placed in this study toward achieving an efficient integration between SFDIA and AFDIA without degradation of performance in terms of false alarm rates and incorrect failure identification. The results of the simulation with different actuator and sensor failures are presented and discussed.

• 제어로봇시스템학회:학술대회논문집
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• 1987.10b
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• pp.161-163
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• 1987

An FTCS is developed for the purpose of improving the reliability of a process control system. The proposed FTCS has capabilities of failure detection, back-up control, graphic display, and self-checking. Also the FTCS is combined with the process simulator to experiment in laboratory for the evaluation of performance of operation. The FTCS is applied to Thermal Power Plant .