• 한국통신학회논문지
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• 제38A권8호
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• pp.623-628
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• 2013

역지향성 배열 안테나 시스템은 기존의 빔형성 기술들에 비하여 복잡도가 낮고 간단하여 시스템 동작 속도가 빠르다. 따라서 고속이동체 환경에서의 빔추적에 용이하다. 하지만 역지향성 배열 안테나는 다중경로 환경 또는 다중 사용자 신호에 따른 AOA(anle of arrival) 추정에 어려움이 있다. 이러한 AOA 추정의 불확실성을 개선 하기 위해 MUSIC 알고리즘과 결합한 디지털 역지향성 배열 안테나 시스템을 제안한다. 본 논문에서는 위상을 추정하는 디지털 PLL 하나를 통하여 위상을 찾는 디지털 역지향성 배열 안테나 시스템을 설계하며 시속 300Km/h의 속도의 이동체를 송수신 거리 100m일때, 원 경로를 따라 움직이는 환경에서의 역지향성 배열 안테나 시스템의 성능을 확인하였고, 다중경로 환경을 고려 하였을 때 시스템의 성능 또한 확인하였다. 고속 추적 모델에 따라AOA를 추적한 결과 10dB의 SNR에서는 오차크기의 평균이 $4.2^{\circ}$, SNR이 20dB인 경우에는 오차크기 평균이 $1.3^{\circ}$이다.

• 정보저장시스템학회:학술대회논문집
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• 정보저장시스템학회 2005년도 추계학술대회 논문집
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• pp.145-149
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• 2005

We describe holographic ROM system to read bit-type data. It has optical system similar to general optical data storage system such as DVD. But because holographic data storage systems have to adopt imaging optical system, in our system bit-type data can be read out by different servos with DVD. We devised 3-hole method similar to 3- beam method for the tracking servo and used astigmatic optical system for the focusing servo. Also we developed the reference beam servo to measure movement of reference beam because especially holographic data storage systems need reference beam. The system was operated by these three servos and objective lens of NA 0.6. We obtained eye pattern from random data of 3T-2um track pitch. We also obtained another eye pattern from DVD disk by only using focusing servo PDIC in our system to verify the compatibility with DVD.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2005년도 춘계학술대회 논문집
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• pp.258-263
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• 2005

Because of its high performance and accuracy, electron beam welding has an important role in industrial applications such as semi-conductor and LCD manufactures. Since its operation has been done in a vacuum room, it is very difficult to check out their weldability as well as the correct welding area of the specimen. In this study, a measurement system of the electron beam welding has been developed based on the 3-axis LVDT controlled table. In addition, the algorithm to tracking the welding line has been developed. Welded regions were measured by using an A-scan ultrasonic sensor only. Weldability of the aluminum specimen has been tested by newly developed measuring system. The results are compared with those by using an C-scan ultrasonic sensor, which show good agreements with each other.

• Applied Science and Convergence Technology
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• 제25권5호
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• pp.98-102
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• 2016

The level set method has recently become popular in the simulation of semiconductor processes such as etching, deposition and photolithography, as it is a highly robust and accurate computational technique for tracking moving interfaces. In this research, full three-dimensional level set simulation has been developed for the investigation of focused ion beam processing. Especially, focused ion beam induced nanodot formation was investigated with the consideration of three-dimensional distribution of redeposition particles which were obtained by Monte-Carlo simulation. Experimental validations were carried out with the nanodots that were fabricated using focused $Ga^+$ beams on Silicon substrate. Detailed description of level set simulation and characteristics of nanodot formation will be discussed in detail as well as surface propagation under focused ion beam bombardment.

• 한국전자파학회논문지
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• 제25권10호
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• pp.1069-1076
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• 2014

본 논문은 능동위상배열 레이더가 여러 개의 표적을 탐지/추적하기에 효과적인 수신빔 구조에 대해 기술하고 있다. 위상배열 레이더가 갖는 특성 중 하나는 원하는 방향으로 빔을 조향하고, 디지털적으로 여러 개의 빔을 동시에 형성하는 것이다. 이와 같은 디지털 빔 형성 수신빔 구조를 통해서 동시 다발적으로 발생하여 접근하는 위협 표적을 빠르고 정확하게 탐지하는 방식을 제안한다. 본 논문에서 제안된 기법들은 시뮬레이션을 통해서 표적의 탐지 정확도 성능을 제시한다.

• International Journal of Aeronautical and Space Sciences
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• 제14권3호
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• pp.282-295
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• 2013

In order to communicate with a ground station, the tracking profile design problem for a directional antenna system is considered. Because the motions of the gimbal angles in the antenna system affect the image quality, the main object is to minimize the motion of the gimbal angles during the satellite's imaging phase. For this goal, parameter optimization problems in the imaging and maneuver phases are formulated separately in the body-frame, and solved sequentially. Also, several mechanical constraints, such as the limitation of the gimbal angle and rate, are considered in the problems. The tracking profiles of the gimbal angles in the maneuver phases are designed with N-th order polynomials, to continuously connect the tracking profiles between two imaging phases. The results confirm that if the vector trace of the desired antenna-pointing vector is within the antenna's beam-width angle, motions of the gimbal angles are not required in the corresponding imaging phase. Also, through numerical examples, it is shown that motion of the gimbal angles in the imaging phase can be minimized by the proposed design process.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.1105-1109
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• 1995

A CCD-camera, which is structured with vision system, was used to realize automatic seam-tracking system and 3-D information which is needed to generate torch path, was obtained by using laser-slip beam. To extract laser strip and obtain welding-specific point, Adaptive Hough-transformation was used. Although the basic Hough transformation takes too much time to process image on line, it has a tendency to be robust to the noises as like spatter. For that reson, it was complemented with Adaptive Hough transformation to have an on-line processing ability for scanning a welding-specific point. the dead zone,where the sensing of weld line is impossible, is eliminated by rotating the camera with its rotating axis centered at welding torch. The camera angle is controlled so as to get the minimum image data for the sensing of weld line, hence the image processing time is reduced. The fuzzy controller is adapted to control the camera angle.

• 대한기계학회논문집A
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• 제24권11호
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• pp.2732-2741
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• 2000

Combination of magnetic recording technology and optical recording technology such as Near Field Optical Recording is watched recently. In order to accomplish this technology, the development of an electromagnetic driven mm-sized mirror shifting laser beam in track direction have to needed. In Near Field Optical Recording System, shifting laser beam in track direction mean as fine tracking and means as coarse tracking. Therefore in Near Field Optical Recording, 2-stage actuator is composed of servo controller in reading or recording information on disc layer. In our research, through design and simulation process of driven mm-sized mirror, we arrange systematically design process of driven mm-sized mirror having good frequency transfer characteristics. Design and simulation processes included modal analysis of spring, calculation of magnetic moment according to the number of turns and geometric configuration of coil and magnetic circuit analysis meaning that calculation of magnetic flux density in air gap of magnetic circuit. After that we design and make parts of driven mm-sized mirror, assemble and evaluate our electriomagnetic driven mm-sized mirror. we compared design values with actual characteristic values and present solution scheme. Through these processes we performed manufacturing of an electromagnetic driven mm-sized mirror having good frequency-domain characteristics and high sensitivity characteristics.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2003년도 추계학술발표대회 개요집
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• pp.18-20
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• 2003

Optimal processing and system to produce the laser welded tube for one body formed bumper beam are studied. The calculated size of tube is a thickness of 1.4mm, diameter of 105.4mm and length of 2000mm. The tube is shaped from cool rolled high strength steel sheet(tensile strength: 60kgf/$\textrm{mm}^2$ grade). Two roll bending method is the optimal tube shaping process compared to UO-bending, bending on press brake, multi-step continuous roll forming and 3 roll bending methods. Weld quality monitoring and seam tracking along the butt-joint lengthwise to the tube axis are also studied. The longitudinal butt-joint is welded by the $CO_2$ laser welding system equipped with a seam tracker and plasma sensor. The constructed $CO_2$ laser tube welding system can be used for the precision seam tracking and the real-time monitoring of weld quality. Finally, the obtained laser welded tube can be used for one-body formed automobile bumper beam.

• 한국광학회지
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• 제16권4호
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• pp.345-353
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• 2005

포토 다이오드(photodiode) 조정 방식을 이용해서, 비전 시스템을 장착한 고가의 정밀 자동 조립조정 장비 없이 홀로그램 픽업 모듈을 제작하는 새로운 방법을 제안하였다. 저가격화를 위해서 리드 프레임형의 반도체 레이저와 COB(Chip on Board)형의 포토 다이오드를 사용했고, 초점 에러 신호(focus error, FES) 검출방법은 스팟 사이즈 검출법(spot size detection, SSD), 트랙 에러 신호(tracking error, TES) 검출방법은 삼빔법(3 beam method)을 이용했다. 이를 만족하는 픽업 홀로그램 모듈 광학계를 설계하고, 조립조정 프로세스 수립 및 시스템을 제작하였으며, 조립된 홀로그램 모듈을 이용하여 CD에서 데이터를 검출하는 실험을 통해 제안된 포토 다이오드 조정방식의 유용함을 입증하였다.