• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.135-136
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• 2006

A precise linear motion stage supported by magnetically preloaded air bearings is introduced where preloading magnetic actuators are combined with permanent magnets and coils to adjust air bearing clearance by controlling magnetic force actively. Each of the magnetic actuators has a permanent magnet generating nominal magnetic flux for required preload and a coil to perturb the magnetic force resulting adjustment of air-bearing clearance. The characteristics of porous aerostatic bearing are analyzed by numerical analysis, and analytic magnetic circuit model is driven for magnetic actuator to calculate nominal preload and variation of force due to current. A 1-axis linear stage motorized with a coreless linear motor and a linear encoder is built for verifying this design concept. With the active magnetic preloading actuators controlled with DSP board and PWM power amplifiers, the active on-line adjusting tests about the vertical, pitching and rolling motion were performed, and the result shows very good linearity.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.773-774
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• 2006

Nowadays, the global interests are concentrated on the preserving of the clean environment, and the diminishing of the dependence on the fossil energy, and among the possible alternative energies, the wind turbine generating system is considered to be the best suited to produce high efficiency energy, without affecting the natural environment. The permanent magnet generators were been used for the wind power generating, for long time, with continuous efforts to improve the generating efficiency. And the latest trend on it is to develop an AFPM(Axial Flux Permanent Magnet)type, which is composed in the structure of rotor and stator shaped in the disc forms, and the direction of the flux at the air gap runs in parallel to the shaft. This thesis is on the study concerning with the analysis of the characteristics of the 5 kW at 300rpm direct drive AFPM generator which is suitable for the small scale wind turbine generating system. In it, the Electro-magnetically Coreless AFPM was been analyzed, the prototype generators been made, concentrated on interpreting the characteristics of the power output, and verifying it through the theoretical study and practical tests.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.12
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• pp.1776-1781
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• 2015

Electric power trains receive electric power from overhead cables via a pantograph system. Power collector system in trains increase the cross section of tunnel and require a massive coreless filter reactor in propulsion inverter because of the power disturbance by contact loss phenomenon of a train. In this paper we proposed a wireless train which can run to next station with charging energy of ultra-capacitor module block. We designed DC-DC converter to charge and discharge ultra-capacitor modules by using Next Train running test results and confirm the feasibility of the proposed system through simulation.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.6
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• pp.134-142
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• 2008

In this paper, we propose a precise linear motion stage supported by magnetically preloaded air bearings. The eight aerostatic bearings with rectangular carbon porous pads were located only one side of vertical direction under the platen where four bearings are in both sides of horizontal direction as wrap-around-design, and this gives simpler configuration than which constrained by air bearings for all direction. Each of the magnetic actuators has a permanent magnet generating static magnetic flux far required preload and a coil to perturb the magnetic farce resulting adjustment of air- bearing clearance. The characteristics of porous aerostatic bearing are analyzed by numerical analysis, and analytic magnetic circuit model is driven for magnetic actuator to calculate preload and variation of force due to current. A 1-axis linear stage motorized with a coreless linear motor and a linear encoder was designed and built to verify this design concept. The load capacity, stiffness and preload force were examined and compared with analysis. With the active magnetic preloading actuators controlled with DSP board and PWM power amplifiers, the active on-line adjusting tests about the vertical, pitching and rolling motion were performed. It was shown that motion control far three DOF motions were linear and independent after calibration of the control gains.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.769-772
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• 2005

Five DOF motion errors of a hydrostatic bearing table driven by the coreless type linear motor were compensated utilizing the active controlled capillaries in this study. Horizontal linear motion and yaw error were simultaneously compensated using two active controlled capillaries and vertical linear motion, pitch and yaw error were also simultaneously compensated using three active controlled capillaries. By the compensation, horizontal linear motion accuracy and yaw were improved from 0.16 ${\mu}m$ and 1.96 arcsec to 0.02 ${\mu}m$ and 0.03 arcsec. Vertical linear motion accuracy, pitch and roll were also largely improved from 0.18 ${\mu}m$, 2.26 arcsec and 0.14 arcsec upto 0.03 ${\mu}m$, 0.07 arcsec and 0.02 arcsec. The compensated motion errors were within the range of measuring repeatability which was ${\pm}0.02\;{\mu}m$ in the linear motion and ${\pm}0.05$ arcsec in the angular motion. From these results, it is found that the motion error compensation method utilizing the active controlled capillaries are very effective to improve the five motion accuracies of the hydrostatic bearing tables.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.10
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• pp.1049-1056
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• 2014

Microelectronics components contain various materials with different coefficients of thermal expansion (CTE). Although a large amount of published data on the CTE of standard materials is available, it occasionally becomes necessary to measure this property for a specific actual material over a particular temperature range. A change in the temperature of a material causes a corresponding change in the output of the strain gage installed on the specimen because of not only the mechanical load but also the temperature change. In this paper, a detailed technique for CTE measurement based on these thermal characteristics of strain gages is proposed and its reliability is evaluated. A steel specimen, aluminum specimen, and copper specimen, whose CTE values are well known, were used in this evaluation. The proposed technique was successfully applied to the measurement of the CTE of a coreless package substrate composing of electronics packages.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.12
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• pp.1303-1312
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• 2013

We report an ultra-precision lathe designed to machine micron-scale features on a large-area roll mold. The lathe can machine rolls up to 600 mm in diameter and 2,500 mm in length. All axes use hydrostatic oil bearings to exploit the high-precision, stiffness, and damping characteristics. The headstock spindle and rotary tooling table are driven by frameless direct drive motors, while coreless linear motors are used for the two linear axes. Finite element method modeling reveals that the effects of structural deformation on the machining accuracy are less than $1{\mu}m$. The results of thermal testing show that the maximum temperature rise at the spindle outer surface is approximately $0.5^{\circ}C$. Finally, performance evaluations of the error motion, micro-positioning capability, and fine-pitch machining demonstrate that the lathe is capable of producing optical-quality surfaces with micron-scale patterns with feature sizes as small as $20{\mu}m$ on a large-area roll mold.

• Research in Plant Disease
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• v.17 no.1
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• pp.95-98
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• 2011

This research was carried out to selection of desirable cultivar for organic cultivation of carrot in Korea. The assay of disease resistance, insect tolerance and rate of bolting were investigated on 32 cultivars of genetic resources of carrot. This experiment was carried out at experimental field and greenhouse of Gangneung-Wonju National University. 'PI 223360' was resistant against powdery mildew. Ten cultivars including 'Oxheart Carrot Heirloom' were moderately resistant, 22 cultivars including 'Long Impeator #58' were susceptible to powdery mildew. Although there was no resistant cultivar against black rot and leaf blight, our results showed that several cultivars have moderate resistance. Thirteen cultivars including 'Oxheart Carrot Heirloom' were having insect (Erythroplusia pyropia) tolerance and 'SA 102' and 'Scarlet Keeper Carrot Rare' were susceptible. According to the investigation of bolting, 6 cultivars including 'Hongsim Ouchon Carrot' were early bolting and 4 cultivars including 'Japanese Imperial Long Carrot' were moderate bolting. Other cultivars were identified as late bolting. From above results, we confirmed that 'Oxheart Carrot Heirloom' was suitable cultivar for organic cultivation among 32 genetic resources of carrot.

• Journal of Aerospace System Engineering
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• v.12 no.2
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• pp.1-6
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• 2018

The torque ripple that is generated by the irregularity of magnetic flux density on the BLDC motor in a satellite actuator degrades the satellite attitude control performance. In this paper, the performance analysis of permanent magnet configurations (shape, arrangement, and air gap) is simulated by the Finite Element Method (FEM) to find the appropriate combination of the configuration. The configuration is chosen by comparing between rectangular and arc-shaped permanent magnets and single-arrangement and dual-arrangement magnets. The performance is verified by a prototype.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.3
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• pp.1-6
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• 2016

The Internet of Things (IoT) is a new technology paradigm demanding one packaged system of various semiconductor and MEMS devices. Therefore, the development of electronic packaging technology with very high connectivity is essential for successful IoT applications. This paper discusses both fan-out wafer level packaging (FOWLP) and 3D stacking technologies to achieve the integrattion of heterogeneous devices for IoT. FOWLP has great advantages of high I/O density, high integration, and design flexibility, but ultra-fine pitch redistribution layer (RDL) and molding processes still remain as main challenges to resolve. 3D stacking is an emerging technology solving conventional packaging limits such as size, performance, cost, and scalability. Among various 3D stacking sequences wafer level via after bonding method will provide the highest connectivity with low cost. In addition substrates with ultra-thin thickness, ultra-fine pitch line/space, and low cost are required to improve system performance. The key substrate technologies are embedded trace, passive, and active substrates or ultra-thin coreless substrates.