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고진공 터보 분자펌프용 자기베어링 시스템의 디지털 선형 제어시스템
노승국,경진호,박종권,남우호,고득용,Ro, Seung-Kook,Kyung, Jin-Ho,Park, Jong-Kweon,Nam, Woo-Ho,Koh, Deug-Yong 한국진공학회 2010 Applied Science and Convergence Technology Vol.19 No.4
본 논문에서는 고진공용 터보분자펌프의 비접촉 고속회전을 위한 자기베어링 시스템의 디지털 제어시스템의 설계에 대하여 소개하였으며, 실례로 800 l/s급의 고진공 펌프에 대하여 축 유연모드의 후방향 위험속도를 넘는 최대 40,000 rpm까지의 회전실험 결과를 나타내었다. 제안된 제어시스템은 기본적으로 PID 기반의 직접궤환 제어기와 자이로스코픽 모멘트 효과를 제어하기 위한 교차궤환기, 유연모우드 감쇄를 위한 리드필터와 동기진동 저감을 위한 노치필터 등으로 구성되어 있으며, 이러한 제어기는 자기부상형 터보분자펌프 외에 고속 플라이휠과 같은 자기베어링에 적용될 수 있다. In this paper, a digital controller of magnetic bearing system for a high vacuum turbomolecular pump (TMP) is designed and examined. For stabilizing and providing damping in magnetic bearing, the digital PID controller is applied for each 5 control axes, and the inter-axis cross feedback controller is also applied to suppress low frequency vibration caused by gyroscopic moment of the rotor at high speed of rotation. The fabricated rotor-shaft has its first flexible natural frequency lower than maximum speed, about 614Hz, so the two lead filters are applied to increase damping of flexible mode. Notch filters with rotating frequency were selected to reduce vibration of the pump housing caused by unbalance load. The implemented controllers are verified by examination of frequency response and rotating test up to 40,000 rpm, which is higher than critical speed of backward flexible mode.
노승국(Seung-Kook Ro),박종권(Jong-Kweon Park),박현덕(Hyun-Duk Park) 한국생산제조학회 2010 한국공작기계학회 추계학술대회논문집 Vol.2010 No.-
This paper introduces recently designed desktop sized NC lathe system and its components. The machine is designed for precision turning of circular parts with 0.5 ~ 20 ㎜ in diameter and length less than 50 mm, with minimum space usage. In this study, it is aimed to achieve high accuracy of the movements and good rigidity of the machine with practical machine, and the components such as main machine structure, spindle and XZ stage were designed to support these performances. The manufactured system has been evaluated for its performances, and some machining examples are shown.
노승국(Seung-Kook Ro),김경호(Gyungho Khim),신우철(Woochul Shin),박종권(Jong-Kweon Park) 한국생산제조학회 2011 한국생산제조시스템학회 학술발표대회 논문집 Vol.2011 No.4
This paper introduces a system to machine micro-sized pat-terns effectively on surface based on micro-milling process using tools with rotation and oscillation. A spindle supported by active magnetic bearings in radial directions were devel-oped and implemented for proposed system. The rotating axis of the tool can be moved faster than stage system up to 500 ㎐ of within air gap as amplitude. This can be applied for repeated patterns without movement of stages carrying workpiece or spindle which have usually slower response time. To review the effectiveness of proposed concept, we integrated the proposed micro-spindle with active magnetic bearings with a precision 3-axis air bearing stage using double-wedge mechanism, and tested this oscillation milling. A flat end mill with 0.8 ㎜ diameter rotating 100 krpm was induced to workpiece with 35 degrees of inclination angle while oscillated 200 ㎐ in radial direction. The results show machined pattern spacing 17 ㎛ and 35 ㎛.
Air-Bag Head 가압식 300㎜ 웨이퍼 폴리싱 테이블의 가압 분포 해석
노승국(Seung-Kook Ro) 한국생산제조학회 2013 한국생산제조학회지 Vol.22 No.2
In this paper, the contact pressure of the wafer and polishing pad for final polishing process for 300 mm-wafer were investigated through numerical analysis using FEM tool, ANSYS. The distribution of the contact pressure is one of main parameters which affects on the flatness and surface roughness of polished wafers. Two types of polishing head, a hard type head with ceramic disk and a soft type head with air bag were considered. The effects of the deformation and initial shape of table on the contact pressure were also examined. Both heads and tables were modeled as 3D finite element model from solid model, and the material properties of polishing pads and rubber plate for the air-bag head were obtained from tensile tests. The contact pressure deviation on wafer surface was smaller with air bag head than hard type head even when the table had form errors such as convex or concave. From this 3D analysis, it could be concluded that the air-bag head has better uniformity of the contact pressure on wafer. Also, the effects of inner diameter of air bag and radial clearance between wafer and retainer were investigated as view point of contact pressure concentration on the edge of wafer.