• 대한기계학회논문집
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• 제19권7호
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• pp.1563-1572
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• 1995

The on-line cure monitoring during the cure process of fiber reinforced resin matrix composite material is important for the better quality and productivity. Among several cure monitoring methods, the dielectrometry that uses electrodes as its sensor is known to be the most promising method. In this study, the sensitivity of the dielectric sensor for the on-line cure monitoring was analyzed by finite element method and compared to the experimental results. Using the analytical results, the equation for the capacitance of the sensor was derived. Also, the optimal sensor design method was suggested after analyzing several different sensor shapes.

• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.1086-1092
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• 2015

The off-line and on-line partial discharge (PD) in the stator winding of three high-voltage (HV) motors (1,400 HP, 6.6 kV) is measured and analyzed in this paper. The off-line PD is measured at high values between 24,300 ~ 36,100 pC after 18 years of motor operation. Spare replacement motors were not available for testing the degree of deterioration of the stator windings in standstill status. Therefore, on-line periodic analysis was conducted to monitor the trend of PD after installing a ceramic sensor (110 pF, 6.6 kV) in the terminal box for each phase of each motor. In the stator winding of the No.1 and No.2 HV motors, which showed high magnitudes of off-line PD and low magnitudes of on-line PD, defects are expected to appear in the neutral end of the winding. On the contrary, in the stator windings of the No.3 HV motor, which exhibits high off-line and on-line PD magnitude, defects are expected to appear in the terminal end of the winding where a voltage close to the phase voltage is applied.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 추계학술발표대회 개요집
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• pp.144-146
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• 2005

Dual electromagnetic sensor is used for sensing the weld line. The sensor consists of excitation and two sensing coil wound over the ferro-magnetic core. By using the dual sensor, the effect of noise is minimized. It is based on the generation of eddy currents in the welding plate by passing current through the excitation coil. The sensor can be used to track the butt joints having no gap between them, where a vision based sensor fails to track. Sensor sensitivity depends on the number of coil turns, frequency of excitation, distance of a sensor from the work piece, diameter of core, etc. The whole system consists of a sensor, a signal processing board, a motion controller and a personnel computer (PC). The raw sensor signal is processed using the signal processing board. It consists of amplification, rectification, filtering, averaging, offset adjustment, etc. Based on sensor data, the motion controller adjusts the position of a welding torch.

• Tribology and Lubricants
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• 제26권1호
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• pp.73-77
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• 2010

One of the important trends for condition monitoring in the 21st century is the development of smart sensors that will permit the cost-effective continuous monitoring of key machine equipments. In this study, an integrated in-line oil monitoring sensor assigned for continuous in situ monitoring multiple parameters of oil performance is presented. The sensor estimates oil deterioration based on the information about chemical degradation, total contamination, water content of oil and oil temperature. The oil oxidation is estimated by "chromatic ratio", total contamination is measured by the changes in optical density of oil in three optical wave-bands ('Red', 'Green' and 'Blue') and water content is evaluated as relative saturation of oil by water. In order to evaluate the sensor's effectiveness, the sensor was applied to several used oil samples in steel making industry and the results were compared with those measured by standard test methods.

• 한국광학회지
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• 제19권1호
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• pp.15-19
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• 2008

크기가 작고 감도가 높은 중공 광섬유를 이용한 In-Line 마이켈슨 간섭계형 전압 센서를 개발하였다. 개발된 In-Line 마이켈슨 갑섭계는 끝 단면은 단일모드광섬유에 연결되어 있고 다른 끝 단면은 깨끗하게 절단된 지름이 4 um의 공기구멍을 가지고 있으며 길이가 10 mm인 중공 광섬유로 구성되어 있다. 개발된 In-Line 마이켈슨 간섭계를 PZT위에 glue를 사용하여 고정시켜 In-Line 마이켈슨 간섭계형 전압 센서를 제작하였다. 제작된 센서는 60 Hz의 AC 전압을 인가하였을 때 출력파형의 주파수는 인가전압의 크기에 비례하였다. 그리고 출력파형의 위상은 인가전압의 크기와 거의 선형적인 관계에 있었으며 센서의 감도는 $0.065{\pi}$ radian/V였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전기설비전문위원
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• pp.103-106
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• 2005

A lot of R&D on the diagnosis of stator winding insolation for large rotating machines has been carried out since the 1970s. The on-line partial discharge measurement has proved to be an effective technique in the evaluation of the state of stator insulation in high voltage rotating machines. The purpose of this paper is to describe the method of the on-line partial discharge measurement on stator windings for hydro- generator with ceramic sensor and measuring system. We developed ceramic coupling sensor, partial discharge measuring system, terminal box and index parameters.

• 정보처리학회논문지C
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• 제14C권1호
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• pp.105-114
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• 2007

센서네트워크 환경에서 이동객체의 위치추적방법은 추적방법론에 따라 데이터의 수신과 위치추적의 정확성에 문제가 있었으며, 이러한 위치데이터는 오로지 위치 추적만을 위한 데이터이었기에 주변의 환경 데이터를 활용하여 상황에 맞는 정보판단 또는 모니터링에 한계가 있었다. 이러한 한계를 극복하기 위한 방법으로 상황인식(context aware)을 종종 활용하는데, 본 문은 자기센서를 기반으로 측정된 자성체(magnetic line tracer)의 자성데이터 위치 추적 및 제어에 관한 데이터처리에 상창인식을 활용한 방법을 제안하였다. 제안된 방법은 센서네트워크 노드의 자기센서의 자성데이터 측정과 주변 환경정보 데이터를 이용하였고, 이러한 데이터를 상황인식 데이터베이스의 엔트리로 구성함으로써 추후 행동정보 추론 및 제어할 수 있다. 아울러 제안된 방법의 타당성을 검증하기 위하여 센서네트워크 환경을 만족하는 테스트베드를 구축하였으며, 이를 이용한 라인트레이서의 위치 추적과 경로탐색의 결과를 도출하였으며, 도출된 데이터를 근거로 하여 주변 환경정보 데이터베이스 엔트리 및 상황인식에 따른 라인트레이서의 방향제어에 미치는 영향을 분석하였다.

• 한국안전학회지
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• 제21권5호
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• pp.40-45
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• 2006

In the operation of large capacity hydro generators, it's a very important thing that to minimize several kind of electrical trouble and accident. In order to overcome these problems, the on-line and off-line partial discharge (PD) measuring method has become an important one. Nowadays, epoxy mica coupler(EMC) has been the most widely used sensors for on-line PD detection in rotating machines. This time, we have made a ceramic coupling sensor using $SrTiO_{3}$, because at present, most of sensors has high cost and difficult procedure to making. This paper deals with the electrical characteristics of a ceramic coupling sensor, which has been made to continuously measure PD activity during the operation condition for 13kV class hydro generator. And we have performed the evaluation of sensor life and reliability based on the characteristic testing. The experimental results confirm that the sensor has satisfied at electrical required performance and output characteristic for simulated input signal.

• 대한산업공학회지
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• 제23권1호
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• pp.95-113
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• 1997

This paper outlines a framework for a diagnosis of a complex system with uncertain information. Sensor validation ploys a vital role in the ability of the overall system to correctly determine the state of a system monitored by imperfect sensors. Here, emphases are put on the heuristic technology and post-processor for reasoning. Heuristic Sensor Validation (HSV) exploits deeper knowledge about parameter interaction within the plant to cull sensor faults from the data stream. Finally the modified probability distributions and validated data are used as input to the reasoning scheme which is the runtime version of the influence diagram. The output of the influence diagram is a diagnostic mapping from the symptoms or sensor readings to a determination of likely failure modes. Once likely failure modes are identified, a detailed diagnostic knowledge base suggests corrective actions to improve performance. This framework for a diagnostic expert system with sensor validation and reasoning under uncertainty applies in $HEATXPRT^{TM}$ a data-driven on-line expert system for diagnosing heat rate degradation problems in fossil power plants [1].

• 한국정밀공학회지
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• 제18권9호
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• pp.179-185
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• 2001

In this study, a visual sensor system for weld seam tracking the I-butt weld joints in GMA welding was constructed. The sensor system consists of a CCD camera, a diode laser with a cylindrical lens and a band-pass-filter to overcome the degrading of image due to spatters and arc light. In order to obtain the enhanced image, quantitative relationship between laser intensity and iris number was investigated. Throughout the repeated experiments, the shutter speed was set at 1-milisecond for minimizing the effect of spatters on the image, and therefore most of the spatter trace in the image have been found to be reduced. Region of interest was defined from the entire image and gray level of searched laser line was compared to that of weld line. The differences between these gray levels lead to spot the position of weld joint using central difference method. The results showed that, as long as weld line was within $^\pm$15$^\circ$from the longitudinal straight fine, the system constructed in this study could track the weld line successful1y. Since the processing time reduced to 0.05 sec, it is expected that the developed method could be adopted to high speed welding such as laser welding.