• 전력전자학회논문지
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• 제20권1호
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• pp.72-80
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• 2015

In distributed generation systems, a grid-connected inverter should operate with synchronization to grid voltage. Considering that synchronization requires the phase angle of grid voltage, a phase locked loop (PLL) scheme is often used. The synchronous reference frame phase locked loop (SRF-PLL) is generally known to provide reasonable performance under ideal grid voltage. However, this scheme indicates performance degradation under the harmonic distorted or unbalanced grid voltage condition. To overcome this limitation, this paper proposes a phase and harmonic detection method of grid voltage using fast Fourier transform (FFT). To reduce the calculation time of FFT algorithm, minimum sampling data is taken from the voltage measurement to determine the phase angle and the magnitude of harmonic components. An experimental test setup for a grid-connected inverter system has been constructed. By comparative simulations and experiments under various abnormal grid voltage conditions, the proposed scheme has been proven to effectively track the phase angle of the grid voltage.

• 로봇학회논문지
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• 제13권1호
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• pp.38-44
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• 2018

In this paper, we propose Intelligent Driver Assistance System (I-DAS) for driver safety. The proposed system recognizes safety and danger status by analyzing blind spots that the driver cannot see because of a large angle of head movement from the front. Most studies use image pre-processing such as face detection for collecting information about the driver's head movement. This not only increases the computational complexity of the system, but also decreases the accuracy of the recognition because the image processing system dose not use the entire image of the driver's upper body while seated on the driver's seat and when the head moves at a large angle from the front. The proposed system uses a convolutional neural network to replace the face detection system and uses the entire image of the driver's upper body. Therefore, high accuracy can be maintained even when the driver performs head movement at a large angle from the frontal gaze position without image pre-processing. Experimental result shows that the proposed system can accurately recognize the dangerous conditions in the blind zone during operation and performs with 95% accuracy of recognition for five drivers.

• 한국정보처리학회논문지
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• 제5권3호
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• pp.824-832
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• 1998

본 논문에서는 영상의 코너점을 추출하기 위한 방법을 제안한다. 먼저 윤곽선을 따라 경계화소의 방향각을 lookup table의 참조에 의해 구하고, 기준치 이상의 화소를 후보점으로 선정한 뒤, 면적편차를 이용하여 코너점을 추출한다. 본 방법은 실시간 처리를 위해 처리시간을 줄이는 동시에 디지털 영상을 표현하는데 있어 라운드 오프 오차에 의해 발생되는 한 화소차를 극복하는 장점을 가진다. 제안된 방법의 검증을 위해 각종 실험 패턴을 이용하여 기존의 방법과 비교분석을 하였다.

• 한국환경과학회지
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• 제30권2호
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• pp.173-184
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• 2021

Ecological disturbance plants distributed throughout the country are causing a lot of damage to us directly or indirectly in terms of ecology, economy and health. These plants are not easy to manage and remove because they have a strong fertility, and it is very difficult to express them quantitatively. In this study, drone hyperspectral sensor data and Field spectroradiometer were acquired around the experimental area. In order to secure the quality accuracy of the drone hyperspectral image, GPS survey was performed, and a location accuracy of about 17cm was secured. Spectroscopic libraries were constructed for 7 kinds of plants in the experimental area using a Field spectroradiometer, and drone hyperspectral sensors were acquired in August and October, respectively. Spectral data for each plant were calculated from the acquired hyperspectral data, and spectral angles of 0.08 to 0.36 were derived. In most cases, good values of less than 0.5 were obtained, and Ambrosia trifida and Lactuca scariola, which are common in the experimental area, were extracted. As a result, it was found that about 29.6% of Ambrosia trifida and 31.5% of Lactuca scariola spread in October than in August. In the future, it is expected that better results can be obtained for the detection of ecosystem distribution plants if standardized indicators are calculated by constructing a precise spectral angle standard library based on more data.

• 한국멀티미디어학회논문지
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• 제9권2호
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• pp.234-243
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• 2006

최근 급속한 HCI(Human-Computer Interaction) 및 감시 기술의 발달로, 얼굴영상을 처리하는 다양한 시스템들에 대한 관심이 높아지고 있다. 그러나 이런 얼굴영상을 처리하는 시스템들에 대한 연구는 주로 얼굴인식이나 얼굴 표정분석과 같은 분야에 집중되었고, 얼굴의 방향성 검출과 같은 분야에는 많은 연구가 수행되지 못하였다. 본 논문은 두 눈썹과 아래 입술로 구성된 얼굴삼각형(Facial Triangle)이라는 특징을 이용하여 얼굴의 방향성을 쉽게 측정하는 방법을 제안한다. 특히, 하나의 이미지만을 사용하여 얼굴의 수평 회전각과 수직 회전각을 구하는 간단한 공식을 소개한다. 수평회전각은 좌 우 얼굴삼각형간의 면적비율을 이용하여 계산하고, 수직회전각은 얼굴삼각형의 밑변과 높이 비율을 이용하여 계산한다. 실험을 통해, 제안하는 방법은 오차범위 ${\pm}1.68^{\circ}$ 내에서 수평회전각을 구할 수 있었고, 수직회전각은 회전각이 증가할수록 오류가 줄어드는 경향을 보여주었다.

• 대한전기학회논문지:시스템및제어부문D
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• 제52권6호
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• pp.333-341
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• 2003

In induction motor control systems driven by the indirect vector control scheme, the rotor speed is measured to determine the flux angle which is a key variable in the control algorithm. The most popular way to measure the angular velocity is the use of rotary encoder. Since the errorneous measurement of rotor speed results in incorrect flux angle estimate, the control input generated based on the faulty information should be far from the desired (correct) value and deteriorates the overall control performance. In this paper the effects of encoder fault on motor variables and control performance are analyzed by both theoretical approach and experimental study. A parity equation based on the Power is suggested and applied to detect the incipient fault of encoder.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.851-856
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• 2003

This paper proposes a single-mode Lamb-wave generation and detection system using a pulsed laser as a generator and an air-coupled transducer combined with the wavelet transform analysis, as the detector. The laser source with arrayed linear slits was used to generate Lamb-wave which is able to control the wavelength of Lamb-wave to be generated by changing the slits separation. An ari-coupled transducer was used to receive Lamb-wave, which can selectably receive a single mode of leaky Lamb wave by changing the oblique angle of transducer, since the leaky Lamb-wave has unique leaky-angle according to the mode. Also, the received signal was processed by wavelet transform for the analysis in domain of time-frequency. The theoretical dipersion curve and the experimetal result was compared to show good agreement.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 춘계학술대회 논문집(한국공작기계학회)
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• pp.61-65
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• 2001

A new flaw detection technique using by SH angle beam method has been discussed. The SH-wave is horizontally polarized shear wave and the surface SH wave has a characteristic of traveling along near surface layer. The surface SH wave technique is valuable for the detection of fatigue cracks at fillet weld heels which cannot be detected by other ultrasonic technique such as angle beam technique and The dispersion curves of it has simple characterization. In this work, using these beneficial chraterization, quality evaluation of spot weld with ultrasonic sound intensity of SH-wave passing through nugget area of spot weld are verified experimentally.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.99-101
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• 2005

This paper deals with drive characteristics of LSRM according to position detection angle. Position of LSRM detected approximation sensor. Position choose mover of LSRM and inductance. When approved current in each phase by decided position, we made sure current and voltage according to turn-on, turn-off.

• 제어로봇시스템학회논문지
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• 제3권6호
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• pp.619-625
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• 1997

In this paper, we show that the rotor position of the bifilar-wound hybrid stepping motors for the closed-loop drives is detected by the phase current measurement. We propose an instantaneous phase current equation, which is the function of electrical angle, by modeling the stepping motor including motor driving circuits. We also analyze the relationship between phase current and rotor position from the computer simulation results. We show that the information about the rotor position is obtained from the phase current amplitude and its derivatives at the instance of ${\pi}/2$ electrical angle of excitation voltage.