• 한국전기전자재료학회논문지
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• 제30권4호
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• pp.229-234
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• 2017

In this study, we fabricated a TFT gas sensor with ZnO nanorods grown by hydrothermal synthesis. The suggested devices were compared with the conventional ZnO film-type TFTs in terms of the gas-response properties and the electrical transfer characteristics. The ZnO seed layer is formed by atomic-layer deposition (ALD), and the precursors for the nanorods are zinc nitrate hexahydrate ($Zn(NO_3)_2{\cdot}6H_2O$) and hexamethylenetetramine ($(CH_2)6N_4$). When 15 ppm of NO gas was supplied in a gas chamber at $150^{\circ}C$ to analyze the sensing capability of the suggested devices, the sensitivity (S) was 4.5, showing that the nanorod-type devices respond sensitively to the external environment. These results can be explained by X-ray photoelectron spectroscopy (XPS) analysis, which showed that the oxygen deficiency of ZnO nanorods is higher than that of ZnO film, and confirms that the ZnO nanorod-type TFTs are advantageous for the fabrication of high-performance gas sensors.

• 전기학회논문지
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• 제63권2호
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• pp.277-283
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• 2014

This paper proposes robot localization using Fuzzy-Extended Kalman Filter algorithm of the mobile robots equipped with least sensors. In order to improve the accuracy of the localization, we usually add the sensors or equipment. However, it increases the simulation time and expenses. This paper solves this problem using only the odometer and ultrasonic sensors to get the localization with the Fuzzy-Extended Kalman Filter algorithm method. By inputting the robot's angular velocity, sensor data variation, and residual errors into the fuzzy algorithm, we get the sensor weight factor to decide the sensor's importance. The performance of the designed method shows by the simulation and Pioneer 3-DX mobile robot test in the indoor environment.

• Structural Monitoring and Maintenance
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• 제1권2호
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• pp.213-230
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• 2014

A novel real-time actuator failure detection algorithm is developed in this paper. Actuator fails when the input to the structure is different from the commanded one. Previous research has shown that one error function can be formulated for each actuator through interaction matrix method. For output without noise, non-zero values in the actuator functions indicate the instant failure of the actuator regardless the working status of other actuators. In this paper, it is further demonstrated that the actuator's error function coefficients will be directly calculated from the healthy input of the examined actuator and all outputs. Hence, the need for structural information is no longer needed. This approach is termed as direct method. Experimental results from a NASA eight bay truss show the successful application of the direct method for isolating and identifying the real-time actuator failure. Further, it is shown that the developed method can be used for real-time sensor failure detection.

• 센서학회지
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• 제13권2호
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• pp.133-138
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• 2004

Today, the obstacle detection system has massive size and restrictive detection range. To solve these problems, this paper proposes the capacitance variation detector using the variated capacitance value as a result of the obstacle approaching. If obstacle approaches, the capacitance value of capacitance sensor is increased and the operating frequency of oscillator is decreased. Then this changed frequency appears to the output of the mixer that operate down conversion. The capacitance variation detector is produced by Hynix$0.35{\mu}$ CMOS process. In experiment result, the frequency of final output is 6.81 MHz at no obstacle and 31.45 MHz at approaching obstacle. In conclusion, proposed capacitance variation detector has small size, low power consumption and easiness to set up anywhere. So it is expected to substitute the obstacle detector.

• 대한조선학회논문집
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• 제42권2호
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• pp.73-79
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• 2005

The characteristics of a tilt sensor utilizing the resistance change of an electrolyte associated with inclination is investigated, and a dynamic compensation modeling is proposed to make the real-time measurement of the absolute slope possible even with sporadically dynamic motion. Although the proposed system is small, economical and accurate for quasi-steady slope measurement, since it contains a freesurface the evolution of the liquid surface that has no direct relation to the real slope must be excluded for any rapid rotations or translations. For various artificial motions the response of the sensor is analyzed and simplified modeling equations are proposed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제3권2호
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• pp.209-218
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• 2009

In a wireless sensor network(WSN) each sensor node deals with numerous sensing data elements. For the sake of energy efficiency and network lifetime, sensing data must be handled effectively. A technique used for this is data aggregation. Sending/receiving data involves numerous steps such as MAC layer control packet handshakes and route path setup, and these steps consume energy. Because these steps are involved in all data communication, the total cost increases are related to the counts of data sent/received. Therefore, many studies have proposed sending combined data, which is known as data aggregation. Very effective methods to aggregate sensing data have been suggested, but there is no means of deciding how long the sensor node should wait for aggregation. This is a very important issue, because the wait time affects the total communication cost and data reliability. There are two types of data aggregation; the data counting method and the time waiting method. However, each has weaknesses in terms of the delay. A hybrid method can be adopted to alleviate these problems. But, it cannot provide an optimal point of aggregation. In this paper, we suggest a stochastic-based data aggregation scheme, which provides the cost(in terms of communication and delay) optimal aggregation point. We present numerical analysis and results.

• 정보처리학회논문지:소프트웨어 및 데이터공학
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• 제6권2호
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• pp.77-84
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• 2017

IoT 환경에서 상황인지 기반 헬스케어 서비스를 제공하기 위해서는 사용자의 건강정보와 주변 환경정보가 필요하다. 환경정보를 구성하기 위해서는 센서데이터를 수집해야 하며, 효과적으로 센서데이터를 수집하기 위해서는 이기종 센서기기의 접근 및 다양한 센서데이터 타입을 일관적으로 처리하기 위한 모델이 필요하다. 센서데이터 수집은 환경정보를 구성하기 위해 선행되어야 하는 과정이며, 이를 통합 처리하기 위한 수집 모델은 아직까지 제안되지 않고 있다. 본 논문에서는 센서데이터의 일관된 수집 및 처리를 위한 이기종 센서데이터 수집 모델을 제안한다. 제안하는 모델은 센서기기 수준에 접근하기 위한 접근정보가 담긴 수집 스키마를 가지며, 제안하는 모델을 통해 이기종 기기의 센서데이터를 일관되게 수집하여 환경정보를 제공할 수 있다. 실험에서는 이기종 센서기기에 접근하기 위한 접근정보와 수집데이터를 명시한 입력 자료를 바탕으로 센서기기에 접근하여 데이터를 수집하는 과정을 보인다.

• 대한원격탐사학회지
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• 제37권5_1호
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• pp.999-1011
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• 2021

다중 센서 영상으로부터 공간 및 시간해상도가 모두 높은 영상을 예측하는 시공간 융합에서 다중 센서 영상의 방사학적 불일치는 예측 성능에 영향을 미칠 수 있다. 이 연구에서는 다중 센서 위성영상의 서로 다른 분광학적 특성을 보정하는 방사보정이 융합 결과에 미치는 영향을 분석하였다. 두 농경지에서 얻어진 Sentinel-2, PlanetScope 및 RapidEye 영상을 이용한 사례연구를 통해 상대 방사보정의 효과를 정량적으로 분석하였다. 사례연구 결과, 상대 방사보정을 적용한 다중 센서 영상을 사용하였을 때 융합의 예측 정확도가 향상되었다. 특히 입력 자료 간 상관성이 낮은 경우에 상대 방사보정에 의한 예측 정확도 향상이 두드러졌다. 분광 특성의 차이를 보이는 다중 센서 자료를 서로 유사하게 변환함으로써 예측 성능이 향상된 것으로 보인다. 이 결과를 통해 상대 방사보정은 상관성이 낮은 다중 센서 위성영상의 시공간 융합에서 예측 능력을 향상시키기 위해 필요할 것으로 판단된다.

• 센서학회지
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• 제28권2호
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• pp.106-112
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• 2019

Flexible impact force sensors composed of piezoelectric PZT/PDMS composite sandwiched between Al/PET films were fabricated and their voltage signal characteristics were evaluated under varying impact forces for electronic mitt applications. The piezoelectric impact force sensor on an ethylene-vinyl acetate (EVA) substrate exhibited an output voltage difference of no greater than 40 mV a periodical impact test in with the impact load was increased by as much as 240 N by a restoration time of 5 s in a five-time experiment, implying good sensing ability. Moreover, the impact force sensor embedded four electronic mitts showed a reliable sensitivity of less than 1 mV/N and good repeatability under 100 N-impact force during a cycle test executed 10,000 times. This indicated that the fabricated flexible piezoelectric impact sensor could be used in electronic mitt applications. However, the relatively low elastic limit of substrate material such as EVA or poly-urethane slightly deteriorated the sensitivity of the impact sensor embedded electronic mitt at over 200 N-impact forces.

• 센서학회지
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• 제1권2호
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• pp.107-116
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• 1992

$CH_{3}CN$ 감지를 위한 최적 모물질은 $CH_{3}CN$의 억분해 온도와 생성량을 적외선 흡수 스펙트럼으로부터 비교함으로써 선정되었다. $SnO_{2}$ 표면에서 $CH_{3}CN$은 $130^{\circ}C$에서부터 열분해되기 시작하여 $300^{\circ}C$에서는 많은 양의 생성물을 생성하였다. 산화반응에 의한 $CH_{3}CN$은 $CO_{2}$, $NH_{3}$ 및 $H_{2}O$로 열분해되었으며, $320^{\circ}C$에서부터 $N_{2}O$가 생성되기 시작하였다. $SnO_{2}$ 감지소자의 $CH_{3}CN$에 대한 감지특성은 $CH_{3}CN$과 금속산화물과의 산화반응으로 인해 생성된 흡착종에 의해 영향을 받았다. 감지물질표면과의 반응에서 생성된 흡착종은 CO, $NH_{3}$, $H_{2}O$ 및 $NO_{x}$ 등이었다. $NO_{x}$의 생성량은 감지특성에 큰 영향을 나타냄을 알 수 있다. 170 ppm의 $CH_{3}CN$에 대한 $SnO_{2}$의 감도와 동작온도는 각각 70% 정도와 $300^{\circ}C$이었다. 0.2wt% Pd 첨가된 $SnO_{2}/Al_{2}O_{3}/Pd$ 감지소자는 $CH_{3}CN$에 대해 높은 감도를 나타내었으며, 응답시간은 약 10초이었다.