• Proceedings of the Korean Society of Precision Engineering Conference
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• 1991.11a
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• pp.101-104
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• 1991

Bal1 screw systems has been used for positioning elements of machine tools. In order to maintain high rigidity and accuracy, preload is applied between nut and screw. However, large amount of preload increases frictional heat. Temperature rises remarkably at high speed notion, Thermal expansion degrades positioning accuracy, In this paper, finite differance method is applied to compute temperature distributions and thermal expansions of ball screw systems according to preload condition and rotational steed. Some simulation results show that the developed methodology is good to study thermal expansion of ball screw systems.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.321-322
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• 2006

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.305-306
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• 2009

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.613-614
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• 2012

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.319-320
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• 2008

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.19 no.3
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• pp.301-308
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• 2001

Nowadays GPS play a important roles in the navigation system of vehicles, but, it doesn't determine the kinematic positions of vehicles accurately because of few satellites in the urban canyon covered with trees and high buildings. So GLONASS (GLObal Navigation Satellites System), the Russian satellites'system, operated in 1996, was introduced to overcome this drawbacks. Therefore, this study deals with the kinematic positioning of vehicles with Real-time code differential positioning methods. As a result, Real-time DGPS/GLONASS is better than Real-time DGPS in the differential corrected positions and HDOP (Horizontal Dilution of Precision). And it was shown that the combined GPS/GLONASS contributes to the precise kinematic positioning of vehicles.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.10
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• pp.45-52
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• 1999

The online realtime positioning error compensation system 'SKY-PACS' is developed to correct geometric errors, thermal errors and tool deflection errors induced by cutting forces on the vertical machining center. 'SKY-PACS' communicates position commands and position compensation signals with the CNC controller at 100Hz, which is CNC control frequency. So the compensation procedure can be applied during axis movement. Using 'SKY-PACS', Maximum 1 axis positioning accuracy was corrected from 5{\mu}m$ to 2{\mu}m$and the squareness error of X-Y table was corrected from 51{\mu}m$/m to below 4{\mu}m$/m. The error compensation under the cutting condition is carried out by ISO10791-7. And the measurement of test-pieces shows that the roundness is corrected rom 8{\mu}m$ to below 5{\mu}m$.

• Journal of Advanced Navigation Technology
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• v.14 no.6
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• pp.783-790
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• 2010

For safety navigation of ships at sea, ships monitor their location obtained from Global Positioning Satellite System (GNSS). In this study, we computed near-real-time positions of a ship at sea using GPS Precise Point Positioning (PPP) technique and analyzed precision of the near-real-time positions. We conducted ship borne GPS observations in the south sea of Korea. To process the GPS data using PPP technique, GIPSY-OASIS (GPS Inferred Positioning System-Orbit Analysis and Simulation Software) developed by the Jet Propulsion Laboratory was used. Antenna phase center variations, ocean tidal loading displacements, and azimuthal gradients of the atmosphere were corrected or estimated as standard procedures of high-precision GIPSY-OASIS data processing. As a result, the precisions of near-real-time positions was ~1cm.

• Journal of the Korea Institute of Military Science and Technology
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• v.4 no.2
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• pp.52-59
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• 2001

In this paper, we have proposed a capability of applying Global Positioning System(GPS) to cannon laying. High precision GPS positioning can be used for measuring precise positions and angles. Therefore, we have tested on applying GPS positioning technique to measurement of positions and angles, which related to cannon laying. First of all, we have determined a GPS reference position using various positioning methods. Then we have carried out several tests that are process of taking corner angles between neighboring two vectors. Each vector can be calculated by post/real time positioning of two GPS antennas placed on the both ends of the howitzer. The Comer Angles from Post processing(CAP) are compared with the other Corner Angles from Real time positioning(CAR). As the results, we have an agreement between CAP and CAR within 0.25 mil average, 0.29 mil standard deviation. Finally, we have discussed about the capabilities and problems in artillery arrangement using GPS.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1344-1348
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• 2003

A precision micro-positioning system with a high displacement resolution and wide motion range has been required for industrialized applications in variety fields. This paper discusses the design of a precision micro-rotation stage with flexure hinges. Proposed system is applied to grinding machine for micro parts. Rotational motion is generated with this system. For this systems having a full rotation motion with high precision, a dual servo system with a coarse stage and a fine stage is proposed.