• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.760-765
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• 2004

One of the obstacles for a magnetic bearing to be used in the wide range of industrial applications is the failure modes associated with magnetic bearings, which we don't expect for conventional passive bearings. These failure modes include electric power outage, power amplifier faults, position sensor faults, and the malfunction of controllers. Fault-tolerant magnetic bearing systems have been proposed so that the system can operate in spite of some faults in the system. In this paper, we designed and implemented a fault-tolerant magnetic bearing system for a turbo-molecular vacuum pump. The system can cope with the actuator/amplifier faults as well as the faults in position sensors, which are the two major fault modes in a magnetic bearing system.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 추계학술대회 논문집
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• pp.304-308
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• 2004

One of the obstacles for a magnetic bearing to be used in the wide range of industrial applications is the failure modes associated with magnetic bearings. These failure modes include power amplifier faults, position sensor faults, and the malfunction of controllers. Fault-tolerant magnetic bearing systems have been proposed so that the system can operate in spite of some faults. In this paper, we designed and tested a fault-tolerant magnetic bearing system. The system can cope with the actuator faults as well as the faults in position sensors, which are the two major fault modes in a magnetic bearing system.

• 대한전기학회논문지:시스템및제어부문D
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• 제53권3호
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• pp.173-181
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• 2004

In normal robot control systems without any actuator failures, it is assumed that actuator torque coefficients applied at each joint have normally 1's all the time. However, it is more practical that actuator torque coefficients applied at each joint are nonlinear time-varying. In other words, it has to be considered that actuators equipped at joints may fail due to hardware or software faults. In this work, actuator torque coefficients are assumed to have non-zero values at all joints. In the case of an actuator torque coefficient which has a zero value at a joint, it means the complete loss of torque on the joint. This paper doesn't deal with the case. As factors of performance degradation of robots, both actuator failures and uncertainties are considered in this paper at the same time. This paper proposes a robust adaptive fault-tolerant control scheme to maintain the required performance and achieve task completion for robot manipulators with performance degradation due to actuator failures and uncertainties. Simulation results are shown to verify the fault tolerance and robustness of the Proposed control scheme.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.363-367
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• 1996

The robustness issues in fault detection and isolation(FDI) have received considerable attenuation in recent years, due to the increasing demand for safe and reliable operation of uncertain and complex dynamic systems. The aim of this paper is to present the FDI method by using proportional integral(PI) observer and unknown input observer(UIO) under the faults of actuators and sensors. Due to this simple residual generator, the PI observer can easily detect the both faults of actuator and sensor. A simulation results show the effectiveness of this methods.

• International Journal of Aeronautical and Space Sciences
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• 제11권2호
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• pp.87-97
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• 2010

A fault tolerant satellite attitude control scheme with a modified iterative learning law is proposed for dealing with actuator faults. The actuator fault is modeled to reflect the degradation of actuation effectiveness, and the solar array-induced disturbance is considered as an external disturbance. To estimate the magnitudes of the actuator fault and the external disturbance, a modified iterative learning law using only the information associated with the state error is applied. Stability analysis is performed to obtain the gain matrices of the modified iterative learning law using the Lyapunov theorem. The proposed fault tolerant control scheme is applied to the rest-to-rest maneuver of a large satellite system, and numerical simulations are performed to verify the performance of the proposed scheme.

• 한국항공우주학회지
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• 제39권2호
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• pp.144-152
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• 2011

본 논문에서는 인공위성 자세제어 시스템의 고장 검출 기법을 제시하였다. 논문에서는 상호간섭 다중모델을 기반으로 벌점을 이용하여 인공위성 자세 시스템 중 구동기의 완전 고장과 구동력 저하 고장을 검출하였다. 제안한 고장 검출 기법은 2단계로 구분되는데, 먼저 11개의 구동기 고장 관련 모델을 구성하여 구동기 고장 검출을 수행한 후, 구동기의 고장이 검출되면 구동기의 고장 특성에 관련된 하위 모델을 생성하여 실제 발생한 고장이 완전 고장인지 구동력 저하 고장인지를 구분하게 된다. 또한 기존에 제안된 상호간섭 다중모델을 이용한 고장 검출 기법과 비교한 결과, 본 논문에서는 병렬로 구성되었던 고장 모델들을 2단계로 구성하고 각 단계별로 차등화된 벌점을 이용함으로써 구동기 고장 검출 시간을 줄였을 뿐만 아니라, 고장의 특성까지 빠르게 구분할 수 있는 장점이 있음을 확인 하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.272-275
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• 1992

A novel fault diagnosis method based on likelihood decomposition is proposed for linear stochastic systems described by autoregressive (AR) model. Assuming that at some time instant .tau. the fault of one of the following two types is occurs: innovation fault (actuator fault); and observation fault (sensor fault), the log-likelihood function is decomposed into two components based on the observations before and after .tau., respectively, Then, the type of the fault is determined by comparing the log-likelihoods corresponding two types of faults. Numerical examples demonstrate the usefulness of the proposed diagnosis method.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.233-238
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• 2000

CNC machine tool is assembled by central processor, PLC(Programmable Logic Controller), and actuator. The sequential control of machine generally controlled by a PLC. The main fault occured at PLC in 3 control parts. In LC faults, operational fault is charged over 70%. This paper describes diagnosis model and data processing for remote monitoring and diagnosis system in machine tools with open architecture controller. Two diagnostic models based on the ladder diagram. Logical Diagnosis Model(LDM), Sequential Diagnosis Model(SDM), are proposed. Data processing structure is proposed ST(Structured Text) based on IEC1131-3. The faults from CNC are received message form open architecture controller and faults from PLC are gathered by sequential data.. To do this, CNC and PLC's logical and sequential data is constructed database.

• 제어로봇시스템학회논문지
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• 제17권10호
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• pp.967-982
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• 2011

This paper presents a FTNCS (Fault-Tolerant Networked Control System) that can tolerate control surface failure and packet delay/loss in an UAV (Unmanned Aerial Vehicle). The proposed method utilizes the benefits of self-diagnosis by smart actuators along with the control allocation technique. A smart actuator is an intelligent actuation system combined with microprocessors to perform self-diagnosis and bi-directional communications. In the event of failure, the smart actuator provides the system supervisor with a set of actuator condition data. The system supervisor then compensate for the effect of faulty actuators by re-allocating redundant control surfaces based on the provided actuator condition data. In addition to the compensation of faulty actuators, the proposed FTNCS also includes an efficient algorithm to deal with network induced delay/packet loss. The proposed algorithm is based on a Lagrange polynomial interpolation method without any mathematical model of the system. Computer simulations with an UAV show that the proposed FTNCS can achieve a fast and accurate tracking performance even in the presence of actuator faults and network induced delays.

• 한국정보과학회논문지:소프트웨어및응용
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• 제35권12호
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• pp.716-730
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• 2008

서비스 지향 아키텍처에서 서비스 제공자는 재사용 가능한 서비스를 개발하고 저장소에 배포하며, 서비스 사용자는 인터페이스를 통하여 블랙박스 컴포넌트 형태의 서비스를 사용한다. 저장소에 배포된 서비스는 시간이 지남에 따라 변경/진화될 가능성이 높고, 다양한 언어 또는 플랫폼을 사용하여 구현되는 이질성(Heterogeneity)을 가진다. 이런 이유로, 서비스 사용자는 서비스 내부 구조를 알기 힘들기 때문에, 서비스가 기능을 수행하는 도중 문제점이 발생하면 문제점을 식별하여 해결하는 등의 서비스 결함을 효과적으로 관리하는 것이 어렵다. 자율 컴퓨팅(Autonomic Computing, AC)은 사람의 개입을 최소화하고 시스템이 스스로의 결함을 관리하도록 설계하는 방식이다. AC는 시스템을 자율적으로 결함을 관리할 수 있는 주요 원칙들을 제안하고 있으므로, 서비스 결함 관리에 관한 기술적 이슈들은 AC의 기법들을 사용하여 해결될 수 있다. 본 논문에서는 SOA 환경에서 자율적으로 서비스의 결함을 관리하기 위한 이론적 모델인 Symptom-Cause-Actuator(SCA) 모델을 제시한다. SCA 모델은 의사가 환자를 치료하는 과정으로부터 유도된다. 먼저, 다섯 단계로 구성된 SCA 컴퓨팅 모델을 정의하고 SCA의 메타모델을 제안한다. 또한, SCA 모델의 저장소 역할을 하는 SCA 프로파일을 정의하고, SCA 프로파일에 저장되는 symptom, cause, actuator의 인스턴스와 이들 간의 의존 관계를 기계가 인식할 수 있는 형식으로 표현한다. 그리고, 서비스의 결함을 자율적으로 관리하는 컴퓨팅 모델의 다섯 단계를 수행하는데 필요한 알고리즘을 상세하게 기술한다. 마지막으로, SCA 모델의 실행 가능성을 보여주기 위하여, SCA 프로파일과 알고리즘을 구현한 프로토타입을 '비행기 예약 시스템'에 적용하는 사례 연구를 수행한다.