• Journal of the Korean Society for Precision Engineering
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• v.31 no.3
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• pp.189-197
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• 2014

Diffractive optical elements (DOEs) - in general a complex pattern of micro- and nano-scale structures - can modulate and transform light in a predetermined way. Their importance is being increased nowadays because they can be designed to handle a number of simultaneous tasks. In view point of machining DOEs, it is a big challenge to fabricate micro- and nano-scale structures on a free-form surfaces. In this paper, the state-of-the-art of the ultra-precision machine tools is reviewed. Also some technical issues which determine the machine tool accuracy are discussed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.4
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• pp.301-307
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• 2015

The diameter of a proton beam emanating from the MC-50 cyclotron is about 2-3 mm with Gaussian distribution. This widely irradiated proton beam is not suitable for semiconductor etching, precise positioning, and micromachining, which require a small spot. In this study, a beam cutting method using a microhole is proposed as an economical alternative. We produced a microhole with aspect ratio, average diameter, and thickness of 428, $21{\mu}m$, and 9 mm, respectively, for cutting the proton beam. By using this high-aspect-ratio microhole, we conducted machinability tests on microstructures with sizes of tens of ${\mu}m$. Additionally, the results of simulation using GEANT4 and those of the actual experiment were compared and analyzed. The outcome confirmed the possibility of implementing a micro process technology for the fabrication of three-dimensional microstructures of 20 micron units using the MC-50 cyclotron with the microhole.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1028-1030
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• 1995

In the fields of the optics, precise machine, semiconducting processing, the micro-positioning actuators are required for the control of position in the submicron range. In this study, $Pb(Ni_{1/3}Nb_{2/3})O_3-Pb({Zn}_{1/3}Nb_{2/3})O_3-Pb({Zr}_{1/2}Ti_{1/2})O_3$ ceramics were fabricated by solid state reaction. The structural, dielectric and electric properties were investigated for sintering condition. The specimen sintered at $1,150(^\circ}C)$ for 1hr, had the highest density and dielectric contant. The resistivity, dielectric and density were increased with increasing PZN contents.

• Proceedings of the KIEE Conference
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• 2003.10b
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• pp.95-97
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• 2003

소형화, 정밀화 되어 가는 산업 추세에 의해 정밀 위치 제어용 엑츄에이터가 요구 되어지고 있다. 이로 인해 생산 및 유지비용이 적은 소형화된 마이크로 위치제어용 엑츄에이터를 개발하였다. 이 엑츄에이터의 설계를 위해서는 해석 기법이 요구되어진다. 그래서 엑츄에이터의 해석 방법을 정식화 하였고, 이를 이용한 해석을 통해 설계를 하였으며 제작을 하였다. 해석방법은 3차원 유한 요소법을 이용하였고, 이를 이용해 소형 마이크로 위치제어용 엑츄에이터의 특성을 해석하였으며, 그 결과는 제작된 엑츄에이터의 실험을 통해 검증되었다. 이 엑츄에이터는 적층 된 압전 세라믹과 두개의 전자석으로 구성되어 있으며, 적층된 압전 세라믹에 의한 변위와 두개의 전자석의 동기화된 동작에 의해 작동이 된다.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.06a
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• pp.42-45
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• 1998

In this paper, a fuzzy control technique using adjustable scale factors and Lyapunov Function for the precise position control of DC servo system is introduced. The suitable scale factors were selected and the stable control input using the stability theory of Lyapunov function cam be applied. Therefore, the controlled system have the robustness against disturbances and can be stabilized because of reinforced adaptivity. This proposed fuzzy controller is implemented on a 80586 micro-computer which have of fuzzy inference routine part, manipulating part of scale factors and DT-2801 data aquisition board.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.446-449
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• 1995

In this paper, the accurate end position control method of ultraprecision machine tool post using piezoelectric material as an micro positonong devics is presented. This method employs the classical PID feedback and uses an additional notch filter which eliminates the resonance characteristics of controlled plant. And the simple predictor is added to make use of the future value of desired input for better tracking performance. To show the feasibilty of proposed method, the PC-based experimental apparacy can be obtained. Using method, Al specimen of diameter 100mm was cut under practical machining condition to test the practicability of proposed method.

• Proceedings of the Korean Information Science Society Conference
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• 2001.04a
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• pp.211-213
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• 2001

본 논문에서는 비대칭적인 인터넷에서의 단방향 지연시간, 지연시간 편차 및 손실률을 측정 할 수 있는 시스템구조를 제시하고, 구현된 측정도구를 이용하여 측정한 결과를 제시한다. 제안된 구조에서는 단방향성 IP 성능 인자의 측정에 반드시 필요한 측정기계들간의 시간 동기화를 위해서 Global Positioning System(GPS)을 이용하여 Micro-second 수준의 정밀도를 제공한다. 그리고, 측정의 정확도를 향상시키기 위하여 송신자 및 수신자가 이더넷 프레임 처리 직전에 시간 정보를 기록하여 프로토콜 계층간의 이동에 의한 지연시간을 줄이고 있다. 본 논문에서는 구현한 측정 도구를 인터넷에 적용하여 단방향성 IP 성능 인자를 얻는다. 또한 이 측정결과를 통해 단방향 측정의 필요성을 제시한다.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.213-216
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• 1996

This paper studies a class of in-parallel manipulators with special geometry where the forward displacement analysis problem can be solved easier than the fully parallel manipulators. Three horizontal links of this mechanism provide 3DOFs(Degrees of Freedom), which are one degree of orientational freedom and two degrees of translatory freedom. Three vertical links of this mechanism provide 3DOFs, which are two degrees of orientational freedom and one degree of translatory freedom. The main advantages of this manipulator, compared with the Stewart platform type, are the capability to produce pure rotation and to predict the motion of the moving platform easily. Since this manipulator has simple kinematic characteristics compared with the Stewart platform, controlling in real-time is possible due to less computational burden. The purpose of this investigation is to develope an analytical method and systematic method to analyze the basic kinematics of the manipulator. The basic kinematic equations of the manipulator are derived and simulation is carried out to show the performance of the mechanism.

• JSTS:Journal of Semiconductor Technology and Science
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• v.2 no.4
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• pp.280-287
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• 2002

We present technical issues involved in the development of actuators and sensors for applications to high-precision Micro Electro Mechanical System (MEMS). The technical issues include fabrication uncertainty and noise disturbance, causing major difficulties for MEMS to achieve high-precision actuation and detection functions. For nano-precision actuators, we solve the fabrication instability and electrical noise problems using digital actuators coupled with nonlinear mechanical modulators. For the high-precision capacitive sensors, we present a branched finger electrodes using high-amplitude anti-phase sensing signals. We also demonstrate the potential applications of the nanoactuators and nanodetectors to high-precision positioning MEMS.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1835-1842
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• 2007

The purpose of this paper describes the changes of TGV & ICE series' nose shape by increasing train speed and according to the periodical characteristics. As the speed increases, the length of the nose shape trends to lengthen longer. But the nose shape length does not increase as speed improves by optimized nose shape to reduce aerodynamic drag and micro-pressure wave in tunnels. TGV & ICE series' nose shape can be classified into Advanced paraboloid type, Shape-nosed type, Organic double-edged type and Flat-nosed type by the advance research(the changes of Shinkansen vehicle' nose shape) of high speed railway. Because it trends to be diversified and characterized more and more. This paper analyzed and introduced as TGV & ICE series' nose shape by top 2 nation (Germany, France) and high speed railway in the past years(1980-2007) for their railway design trends by new positioning(Advance research).