• International Journal of Air-Conditioning and Refrigeration
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• 제9권3호
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• pp.63-71
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• 2001

This paper presents a model-based method for detecting and diagnosing some faults in the cooling tower of healing, ventilating, and air-conditioning systems. A simple model for the cooling tower is employed. Faults in cooling tower operation are detected through the deviations in the values of system characteristic parameters such as the heat transfer coefficient-area product, the tower approach, the tower effectiveness, and fan power. Three distinct faults are considered: cooling tower inlet water temperature sensor fault, cooling tower pump fault, and cooling tower fan fault. As a result, most values of the system characteristics parameter variations due to a fault are much higher or lower than the values without faults. This allows the faults in a cooling tower to be detected easily using above methods. The diagnostic rules for the faults were also developed through investigating the changes in the different parameter due to each faults.

• 소음진동
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• 제10권6호
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• pp.985-990
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• 2000

The signals that can be obtained from rotating machines often convey the information of machine. For example, if the machine under investigation has faults, then these signals often have pulse signals, embedded in noise. Therefore the ability to detect the fault signal in noise is major concern of fault diagnosis of rotating machine, In this paper, minimum variance cepstrum (MV cepstrum) . which can easily detect impulse in noise, has been applied to detect the type of faults of ball bearing system. To test the performance of this technique. various experiments have been performed for ball bearing elements that have man made faults. Results show that minimum variance cepstrum can easily detect the periodicity due to faults and also shows the pattern of excitation by the faults.

• 제어로봇시스템학회논문지
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• 제10권8호
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• pp.748-754
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• 2004

In this paper, we propose the Triple Modular Redundancy (TMR) control system equipped with a checkpoint strategy. In this system, faults in a single processor are masked and faults in two or more processors are detected at each checkpoint time. When faults are detected, the rollback recovery is activated to recover from faults. The conventional TMR control system cannot overcome faults in two or more processors. The proposed system can effectively cope with correlated and independent faults in two or more processors. We develop a reliability model for this TMR control system under correlated and independent transient faults, and derive the reliability equation. Then we investigate the number of checkpoints that maximizes the reliability.

• 전자공학회논문지C
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• 제34C권1호
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• pp.1-11
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• 1997

A BiCMOS circuit consists of the CMOS part which performs the logic function, and the bipolar part which drives output load. In BiCMOS circuits, transistor stuck-open faults exhibit delay faults in addition to sequential beavior. Also, stuck-on faults enhanced IDDQ (quiscent power supply current) at steady state. In this paper, a method is proposed which efficiently generates test patterns to detect stuck-open faults and stuck-on faults in BiCMOS circuits. The proposed method divides the BiCMOS circuit into pull-up part and pull-down part, and generates test patterns detect faults occured in each part by structural property of the BiCMOS circuit.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.826_827
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• 2009

This paper introduces major potential faults of Poly-Phase Permanent Magnet Synchronous Motor and their simulation realization methods. The faults of Poly-Phase PM Synchronous Motor, generally, stator turn faults, demagnetizing field. Based on the derived expressions, Poly-Phase PM synchronous Motor simulation model, which is capable of representing stator turn faults, is implemented in Maxwell.

• 전자공학회논문지SC
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• 제48권3호
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• pp.40-47
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• 2011

본 논문에서는 상태 피드백 제어를 이용한 비동기 순차 머신의 고장 탐지 및 극복 과정을 다룬다. 논문에서 고려하는 비동기 머신은 간헐 고장의 영향을 받는다. 간헐 고장이 발생하면 머신은 원하지 않는 상태 천이를 하며, 일정 시간 동안 외부 입력의 변화에 반응하지 못하고 고장 상태를 유지한다. 본 논문에서는 비동기 머신에서 발생하는 간헐 고장을 탐지할 수 있는 조건을 규명하고 간헐 고장을 극복하는 견실한 상태 피드백 제어기의 존재조건과 설계 알고리듬을 제안한다. 과도 고장에 대한 기존의 내고장성 제어 기법과 이번 연구에서 제안하는 간헐 고장에 대한 제어기 동작과의 차이점도 설명한다. 또한 사례 연구를 통해서 제안된 제어기의 설계 과정을 예시한다.

• Smart Structures and Systems
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• 제29권6호
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• pp.785-790
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• 2022

Condition monitoring of permanent magnet synchronous motors (PMSMs) and detecting faults such as eccentricity and demagnetization are essential for ensuring system reliability. Motor current signal analysis is the most commonly used precursor for detecting faults in the PMSM drive system. However, the current signature responds sensitively to the load and temperature of the motor, thereby making it difficult to monitor faults in real- applications. Therefore, in this study, a condition monitoring methodology that detects motor faults, including their classification with standstill conditions, is proposed. The objective is to detect and classify faults of PMSMs by using programmable inverter without additional sensors and systems for detection. Both DC and AC were applied through the d-axis of a three-phase motor, and the change in incremental inductance was investigated to detect and classify faults. Simulation with finite element analysis and experiments were performed on PMSMs in healthy conditions as well as with eccentricity and demagnetization faults. Based on the results obtained from experiments, the proposed method was confirmed to detect and classify types of faults, including their severity.

• 조명전기설비학회논문지
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• 제18권5호
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• pp.132-139
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• 2004

수배전계통의 고장에는 1선 지락, 선간 단락, 2선 지락 등의 고장이 있다. 가공 배전 계통에서 일어나는 대부분의 고장은 1선 지락이며, 피뢰기는 이러한 고장에 의한 빈번한 과전압에 의해 스트레스를 받는다. 본 논문에서는 수배전계통에서 일어날 수 있는 고장을 모의하여 여러 가지 고장에 의해 피뢰기에 흐르는 누설전류의 특성에 대하여 조사하였다. 결과적으로, $\pm$10[%] 범위의 전압변동률에 의해서 피뢰기에 흐르는 누설전류는 거의 변화가 없었다. 성능이 우수한 접지 시스템 하에서는 전압변동률은 피뢰기의 긴 시간동안의 동작에 별 영향을 줄 수가 없었다. 하지만, 1선 지락 고장에서 피뢰기에 흐르는 누설전류의 최대값은 비효과적인 접지 시스템의 운전 전압에서의 누설전류와 비교하였을 때 140배 이상이 되었다. 그러나 선간 단락과 2선 지락 고장의 경우에는 피뢰기의 누설전류에 거의 영향을 미치지 못했다.

• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.886-889
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• 2017

An active Fault Tolerant Model Predictive Control (FTMPC) using Fuzzy scheduler is developed. Fault tolerant Control (FTC) system stages are broadly classified into two namely Fault Detection and Isolation (FDI) and fault accommodation. Basically, the faults are identified by means of state estimation techniques. Then using the decision based approach it is isolated. This is usually performed using soft computing techniques. Fuzzy Decision Making (FDM) system classifies the faults. After identification and classification of the faults, the model is selected by using the information obtained from FDI. Then this model is fed into FTC in the form of MPC scheme by Takagi-Sugeno Fuzzy scheduler. The Fault tolerance is performed by switching the appropriate model for each identified faults. Thus by incorporating the fuzzy scheduled based FTC it becomes more efficient. The system will be thereafter able to detect the faults, isolate it and also able to accommodate the faults in the sensors and actuators of the Continuous Stirred Tank Reactor (CSTR) process while the conventional MPC does not have the ability to perform it.

• International Journal of Aeronautical and Space Sciences
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• 제17권1호
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• pp.54-63
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• 2016

A novel attitude tacking control method using Time Delay Control (TDC) scheme is developed to provide robust controllability of a rigid hexacopter in case of single or multiple rotor faults. When the TDC scheme is developed, the rotor faults such as the abrupt and/or incipient rotor faults are considered as model uncertainties. The kinematics, modeling of rigid dynamics of hexacopter, and design of stability and controllability augmentation system (SCAS) are addressed rigorously in this paper. In order to compare the developed control scheme to a conventional control method, a nonlinear numerical simulation has been performed and the attitude tracking performance has been compared between the two methods considering the single and multiple rotor faults cases. The developed control scheme shows superior stability and robust controllability of a hexacopter that is subjected to one or multiple rotor faults and external disturbance, i.e., wind shear, gust, and turbulence.