• 대한전자공학회논문지SD
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• 제41권11호
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• pp.97-104
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• 2004

본 논문은 JPEG2000의 손실 압축 또는 무손실 압축에 사용되어지는 9-7/5-3 리프팅 DWT필터에 대한 효율적인 VLSI 구조를 제안한다. 제안된 구조는 리프팅 DWT 연산을 위해 내부 라인 메모리만을 사용하며, 내부 처리 유닛은 1개의 곱셈기와 1개의 덧셈기의 임계경로를 갖는다. 특히 본 논문에서는 처리유닛의 수를 감소하기 위해 1레벨의 열방향을 담당하는 필터로 하여금 2레벨 이상의 행방향과 열방향 연산 모두를 처리하도록 하였다. 결과적으로 제안된 구조는 기존의 구조에 비해 작은 하드웨어 크기를 갖는다. 제안된 리프팅 DWT구조는 RTL 수준에서 VHDL로 모델링되었으며, 기능 검증 후 Altera APEX 20K FPGA로 구현되었다.

• 한국정밀공학회지
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• 제15권5호
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• pp.93-99
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• 1998

Although laser interferometer measurement system has advantages of measurement range and accuracy, it has some disadvantages when measurement of multi degrees of freedom of motion are required. Because the traditional error measurement methods for geometric errors (two straightness and three angular errors) of a slide of machine tools measures error components one at a time. It may also create an optical path difference and affect the measurement accuracy. In order to identify and compensate for geometric errors of a moving rigid body in real time processes, an on-line error measurement system for simultaneous detection of the five error components of a moving object is required. Using laser alignment technique and some optoelectronic components, an on-line measurement system with 5 degrees of freedom was developed for the geometric error detection in this study Performance verification of the system has been performed on an error generating mechanism. Experimental results show the feasibility of this system for identifying geometric errors of a slide of machine tools.

• 한국CDE학회논문집
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• 제5권2호
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• pp.144-154
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• 2000

We propose an algorithm for obtaining a triangular approximation of a trimmed NLRBS surface. Triangular approximation is used in the pre-processing step of many applications such as RP(Rapid Prototyping), NC(Numerical Control) and FEA(Finite Element Analysis), etc. The algorithm minimizes the number of triangular elements within tolerance and generates a valid triangular mesh for STL file and NC tool path generation. In the algorithm, a subdivision method is used. Since a patch is a basic element of triangular mesh creation, boundary curves of a patch are divided into line segments and the division of curves is applied for the interior of the surface. That is, boundary curves are subdivided into line segments and two end points of each line segment are propagated to the interior of the surface. For the case of a trimmed surface, triangulation is carried out using a model space information. The algorithm is superior because the number of elements can be controlled as the curvature of the surface varies and it generates the triangular mesh in a trimmed region efficiently. To verify the efficiency, the algorithm was implemented and tested for several 3D objects bounded by NURBS surfaces.

• 한국정밀공학회지
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• 제26권6호
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• pp.50-58
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• 2009

Micro laser fabrication techniques can potentially be used for the manufacture of microstructures on the thin flat surfaces with large diameter that are frequently used in semiconductor industries. However, the large size of wafers can cause the degraded machining accuracy of the surface because it can be tilted or distorted by geometric errors of machines or the holding fixtures, etc. To overcome these errors the off-line focusing error compensation method is proposed. By using confocal autofocus system, the focusing error profile of machined surface is measured along the pre-determined path and can be compensated at the next machining process by making the corrected motion trajectories. The experimental results for silicon wafers and invar flat surfaces show that the proposed method can compensate the focusing error within the level of below $6.9{\mu}m$ that is the depth of focus required for the laser micromachining process.

• Journal of information and communication convergence engineering
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• 제7권3호
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• pp.366-371
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• 2009

A realization for an accurate position detecting system of a moving target in two dimensional plane using dual line CCDs and photometric interpolation is presented. The system is realized that the infrared LEDs are utilized for lighting source, a target size is recognized by the scanned data from CCD owing to blocking the radiated light path by placing the target between CCD and lighting source, a coordinate on the plane is found by plane trigonometry formed by the moving target and two CCD sensors, and the former scan data is used for the coordinate iteratively and the photometric interpolation is applied to sub-pixel of scanned image. The experimental results show that the experiment results in a success rate about 3 different size targets, 3, 5 and 7mmm on the test plane $210{\times}373mm$. The moving target positioning detected success rate is 93% in 3mm target, 5mm is 95.3%, and 7mm is 95.8% respectively. The photometric interpolation is enhanced to 1.5% in comparison to be unused.

• 한국광학회지
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• 제17권2호
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• pp.159-164
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• 2006

원통형의 압접소자를 이용한 광지연선을 사용하여 광 간섭형 단층촬영 시스템을 제작하였다. 광지연선은 18 m 길이의 단일 모드 광섬유를 압전소자의 둘레에 134회 감아 구성하였으며 0.78 mm의 광경로 길이변화를 얻었다. 제작한 광 간섭형 단층촬영 시스템은 신호 대 잡음비 96.9 dB, 종방향 분해능 $18.6{\pm}0.5\;{\mu}m$, 횡방향 분해능 $5\;{\mu}m$의 특성을 보였다.

• 전기학회논문지
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• 제64권5호
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• pp.708-717
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• 2015

This paper proposes a new reduction scheme of circulating current when two units of BESS (Battery Energy Storage System) are operated in parallel with conventional droop control. In case of using conventional droop, the terminal voltage of each BESS are not equal due to the unequal line impedance, which causes the circulating current. The operation performance of BESS is critically dependant on the circulating current because it increases system losses which causes the increasement of required system rating. This paper introduces a new reduction scheme of circulating current in which the terminal voltage difference of each BESS is compensated by adding feed-forward path of line voltage drop to the droop control. The feasibility of proposed scheme was first verified by computer simulations with PSCAD/EMTDC software. After then a hardware prototype with 5kW rating was built in the lab and many experiments were carried out. The experimental results were compared with the simulation results to confirm the feasibility of proposed scheme. Two parallel operating BESS with proposed scheme shows more accurate performance to suppress the circulating current than those with the conventional droop control.

• Current Optics and Photonics
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• 제3권1호
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• pp.16-21
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• 2019

We present a broad-bandwidth comb-spacing-swept source (CSWS) based on a differential polarization delay line (DPDL) for interferometric three-dimensional (3D) imaging. The comb spacing of the CSWS is repeatedly swept by the tunable DPDL in the multiwavelength source to provide depth-scanning optical coherence tomography (OCT). As the polarization differential delay of the DPDL is tuned from 5 to 15 ps, the comb spacing along the wavelength continuously varies from 1.6 to 0.53 nm, respectively. The wavelength range of various semiconductor optical amplifiers and the cavity feedback ratio of the tunable fiber coupler are experimentally selected to obtain optimal conditions for a broader 3-dB bandwidth of the multiwavelength spectrum and thus provide a higher axial resolution of $35{\mu}m$ in interferometric OCT imaging. The proposed CSWS-OCT has a simple imaging interferometer configuration without reference-path scanning and a simple imaging process without the complex Fourier transform. 3D surface images of a via-hole structure on a printed circuit board and the top surface of a coin were acquired.

• 한국산학기술학회논문지
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• 제15권1호
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• pp.466-474
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• 2014

본 논문에서는 여러 가지 광 스위치들의 기능, 구조 및 장단점들을 비교 분석하여 이를 토대로 광 스위치를 선택하고, 이 스위치 모듈에 있는 파장변환기를 이용하여 블록킹을 피하기 위한 회선 경합 회피 스위칭 실험을 하였다. 스위치 패브릭의 성능을 평가하는 기본적인 기준은 넌블록킹(nonblocking), 모듈성(modularity), 업그레이드 능력(upgrade ability) 그리고 광 손실(power loss)인데 이들을 종합적으로 분석 평가하여 스위치를 선택하였다. 이렇게 선택된 스위치 패브릭은 블록킹 발생을 피하기 위한 3가지의 경우에 대하여 파장 변환을 통한 스위칭을 함으로써 회선경합 회피를 할 수 있음을 보여주었다. 이 실험의 결과는 파장 변환기의 제어를 통하여 경로를 바꾼 광신호가 출력단에서 바뀐 광파워(power)의 피크임을 보여줌으로써 라인 경합을 피하여 스위칭 되었음을 확인하였다. 또한 스위치보드에서 시간에 따른 광 파워의 변화를 분석하여 스위칭에 필요한 스위치의 채널 설정 시간과 해제 시간을 알아내었다. 이에 대한 분석 결과를 망설계시 반영하면 경제적이고 효율적인 네트워크 구조로 디자인할 수 있다.

• Ocean and Polar Research
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• 제33권1호
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• pp.69-76
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• 2011

A test miner named MineRo was constructed for the purpose of shallow water test of mining performance. In June of 2009, the performance test was conducted in depth of 100 m, 5 km away from Hupo-port (Korean East Sea), to assess if the developed system is able to collect and lift manganese nodules from seafloor. In August of 2010, in-situ test of automatic path tracking control of MineRo was performed in depth of 120 m at the same site. For path tracking control, a localization algorithm determining MineRo's position on seabed is prerequisite. This study proposes an improved underwater navigation algorithm through estimation of MineRo's kinematic parameters. In general, the kinematic parameters such as track slips and slip angle are indirectly calculated using the position data from USBL (Ultra-Short Base Line) system and heading data from gyro sensors. However, the obtained data values are likely to be different from the real values, primarily due to the random noise of position data. The aim of this study is to enhance the reliability of the algorithm by measuring kinematic parameters, track slips and slip angle.