• 한국의학물리학회지:의학물리
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• 제7권1호
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• pp.3-7
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• 1996

정위적 방사선수술을 시행하기 위하여 CT, MR, 그리고 digital angiography 의 표적 위치결정의 정확도를 평가하였다. 특정한 지점의 위치가 이미 알려져 있는 (정밀도 : 0.lmm 이내) geometrical phantom 을 CT 혹은 MR로 scan 하였다. Scan 간격은 3mm 이었으며 FOV (Field of View)는 CT의 경우 35cm, MR 의 경우 28cm 이었다. 얻어진 영상은 GE format 의 형태로 TCP/IP를 이용하여 치료계획 컴퓨터로 전달되었다. 각 영상을 컴퓨터로 분석하여 얻은 측정된 좌표값을 이미 알고 있는 값과 비교하였다. Digital angiography 의 경우, 좌표값을 결정하기 위하여 anterior-posterior 방향과 lateral 방향의 film을 얻었으며 이 film은 film scanner를 이용하여 치료계획 컴퓨터로 전달되었다. CT 영상의 위치결정 오차는 1.2$\pm$0.5 mm이었으며 MR의 경우에는 coronal 및 sagittal 영상에 대하여 각각 평균 1.7$\pm$0.4mm, 2.1$\pm$0.7mm의 오차가 있었다. 반면에 Axial 영상의 경우에는 오차가 평균 4.7$\pm$ 0.9mm이었다. Digital angiography 의 위치결정 오차는 0.9$\pm$0.4mm이었다. CT, MR, 그리고 Angiography 등과 같은 진단장비를 이용하여 표적의 위치 및 형태를 정의하는데 있어서의 정확도는 진단 영상의 분해능 및 distortion 과 밀접한 관련을 가지고 있다. CT의 경우, 위치결정 오차는 주로 영상의 slice 간격에 따른 분해능에 의존하며 MR 영상의 경우에는 영상자체의 분해능과 더불어 head frame에 의한 distortion이 크게 작용하였다. 반면에 Digital angiography의 경우에는 fiducial marker의 distortion으로 인한 오차가 가장 크게 영향을 주었다. 본 연구의 결과는 치료계획시 PTV(Planning Target Volume)를 결정할 때 반드시 고려되어야 한다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.956-959
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• 2004

Recently the monitoring system of tool setting in high speed precision machining center is required for manufacturing products that have highly complex and small shape, high precision and high function. It is very important to reduce time to setup tool in order to improve the machining precision and the productivity and to protect the breakage of cutting tool as the shape of product is smaller and more complex. Generally, the combination of errors that geometrical clamping error of fixing tool at the spindle of machining tool and the asynchronized error of driving mechanism causes that the run-out of tool reaches to 3$^{\sim}$20 times of the thickness of cutting chip. And also the run-out is occurred by the misalignment between axis of tool shank and axis of spindle and spindle bearing in high speed rotation. Generally, high speed machining is considered when the rotating speed is more than 8,000 rpm. At that time, the life time of tool is reduced to about 50% and the roughness of machining surface is worse as the run-out is increased to 10 micron. The life time of tool could be increased by making monitoring of tool-setup easy, quick and precise in high speed machining tool. This means the consumption of tool is much more reduced. And also it reduces the manufacturing cost and increases the productivity by reducing the tool-setup time of operator. In this study, in order to establish the concept of tool-setup monitoring the measuring method of the geometrical error of tool system is studied when the spindle is stopped. And also the measuring method of run-out, dynamic error of tool system, is studied when the spindle is rotated in 8,000${\sim}$60,000 rpm. The dynamic phenomena of tool-setup are analyzed by implementing the monitoring system of rotating tool system and the non-contact measuring system of micro displacement in high speed.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.1066-1069
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• 2004

Recently the monitoring system of tool setup in high speed precision machining tool is required for manufacturing products that have highly complex and small shape, high precision and high function. It is very important to reduce time to setup tool in order to improve the machining precision and productivity and to protect the breakage of cutting tool as the shape of product is smaller and more complex. Generally, the combination of errors that geometrical clamping error of fixing tool at the spindle of machining center and the asynchronized error of driving mechanism causes that the run-out of tool reaches to 3∼20 times of the thickness of cutting chip. And also the run-out is occurred by the misalignment between axis of tool shank and axis of spindle and spindle bearing in high speed rotation. Generally, high speed machining is considered when the rotating speed is more than 8,000 rpm. At that time, the life time of tool is reduced to about 50％ and the roughness of machining surface is worse as the run-out is increased to 10 micron. The life time of tool could be increased by making monitoring of tool-setting easy, quick and precise in high speed machining center. This means the consumption of tool is much more reduced. And also it reduces the manufacturing cost and increases the productivity by reducing the tool-setup time of operator. In this study, in order to establish the concept of tool-setting monitoring the measuring method of the geometrical error of tool system is studied when the spindle is stopped. And also the measuring method of run-out, dynamic error of tool system, is studied when the spindle is rotated in 8,000 ∼ 60,000 rpm. The dynamic phenomena of tool-setup is analyzed by implementing the monitoring system of rotating tool system and the noncontact measuring system of micro displacement in high speed.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.355-360
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• 2002

To calibrate a non-redundantly actuated parallel mechanism, one can find actual kinematic parameters by means of geometrical constraint of the mechanism's kinematic structure and measurement values. However, the calibration algorithm for a non-redundant case does not apply fur a redundantly actuated parallel mechanism, because the angle error of the actuating joint varies with position and the geometrical constraint fails to be consistent. Such change of joint angle error comes from constraint torque variation with each kinematic pose (meaning position and orientation). To calibrate a redundant parallel mechanism, one therefore has to consider constraint torque equilibrium and the relationship of constraint torque to torsional deflection, in addition to geometric constraint. In this paper, we develop the calibration algorithm fir a redundantly actuated parallel mechanism using these three relationships, and formulate cost functions for an optimization algorithm. As a case study, we executed the calibration of a 2-DOF parallel mechanism using the developed algorithm. Coordinate values of tool plate were measured using a laser ball bar and the actual kinematic parameters were identified with a new cost function of the optimization algorithm. Experimental results showed that the accuracy of the tool plate improved by 82% after kinematic calibration in a redundant actuation case.

• 한국산학기술학회논문지
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• 제20권4호
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• pp.464-469
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• 2019

테이퍼 롤러 베어링은 큰 부하 하중이 가해져도 안정적으로 차량을 지지할 수 있어서 승합차, 화물차, 열차 등에 핵심적인 구동 부품으로 광범위하게 사용된다. 테이퍼 롤러 베어링 부품 중에서 케이지는 롤러들 사이의 간격을 유지해 주며, 이를 통해서 마찰 방지 및 마모, 발열을 억제하고 윤활을 위한 공간을 제공해주는 등의 역할을 한다. 차량이 주행 중에 공진으로 인해 케이지가 심하게 변형되면 롤러가 원활한 구름 운동을 하지 못하거나, 케이지를 이탈하는 경우가 발생하게 된다. 따라서 베어링의 안정적인 내구성능을 확보하기 위해서는 케이지의 공진주파수를 파악하는 것이 매우 중요하다. 베어링 케이지는 구조적으로 동일한 형상이 반복되는 주기적 구조물로 볼 수 있는데, 이러한 구조물은 제작과정에서 설계 시 의도한 완벽한 기하학적 형상과는 어느 정도의 오차를 가진 형상으로 제작되게 된다. 본 연구에서는 이러한 케이지의 기하학적 불완전성이 동특성에 미치는 영향을 파악하고자 한다. 그 결과 기하학적인 불완전성에 의하여 이상적인 케이지의 고유진동수 부근에서 고유진동수 분리가 발생하며, 그 간격은 기하학적 오차의 크기에 비례하고 모드의 차수가 증가할수록 그 간격도 넓어진다고 판단된다.

• 한국기계가공학회지
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• 제6권3호
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• pp.53-57
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• 2007

This paper presents a geometrical error compensation of tool alignment for B axis controlled machine. In precision machining, tool alignment is crucial parameter for machined surface. To decrease tool alignment error, plus tilted tool from B axis center is touched to reference work piece and checked the deviation from original position. Same process is performed in minus tilt. Comparing these 2 touch positions, wheel alignment error in X axis and Z axis can be calculated on B axis center. Experimental results show that this compensation method is efficient to correct tool alignment.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 추계학술대회 논문집 학회본부
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• pp.38-41
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• 1997

As the LPM is used for position accuracy decision device it is required that both the reason of posion error and the definition of position itself should be cleared. In this study, the precision of the position decision of LPM is affected by the geometrical shape such as tooth shape or processing accuracy. By using the analysis of magnetic circuit, we calculated the permeance come up with the gap. Once the thrust force has been obtained, the permeance due to the mechanical error of the pole pitch and the tooth pitch becomes the error of thrust force. We confirmed as well that it is being affected by the difference due to the variation of the airgap permeance.

• 대한기계학회논문집A
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• 제25권9호
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• pp.1317-1324
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• 2001

In this paper, a methodology of geometrical error identification and compensation for NC machine tool position is developed. We propose a reference artifact with measuring the geometry of coordinate system for compensating linear scale error of NC machine. The coordinate system of the NC machine could be compensated successfully with the information obtained by measuring the reference artifact and our compensation algorithm. Monte Carlo simulation is used to evaluate coordinate referencing ability and, the uncertainties of the machine tool position is estimated and observed through the compensation process by simulation.

• 한국정밀공학회지
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• 제14권1호
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• pp.90-100
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• 1997

Sppur gear trains are used widely in high precision machines because gear trains have an advantage of exact transmission of angular velocity. Especially, gear trains are used in high quali8ty photocopying and photography OA machines. In general, gears have errors in manufacturing and assembling process and the errors are limited by tolerances. As the result, the tolerances cause the performance error. Therfore, it is important to predict transmission error caused by the tolerances for the tolerance design. Earlier tolerance design methods use mainly experimental and geometrical techniques. In this paper, a method for gear train analysis with tolerance is proposed. Because the method uses dynamic contacts, it is possible to consider irregularities and assemble errors of gears. In addition, the method can predit dynamic loads on the teeth of gears.

• 제어로봇시스템학회논문지
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• 제18권5호
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• pp.502-508
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• 2012

Heliostat, as a concentrator to reflect the incident solar energy to the receiver, is the most important system in the tower-type solar thermal power plant since it determines the efficiency and ultimately the overall performance of solar thermal power plant. Thus, a good sun tracking ability as well as a good optical property of it are required. Heliostat sun tracking system uses usually an open loop control system. Thus the sun tracking error caused by heliostat's geometrical error, optical error and computational error cannot be compensated. Recently use of sun tracking error model to compensate the sun tracking error has been proposed, where the error model is obtained from the measured ones. This work is a development of heliostat sun tracking error measurement and compensation method using BCS (Beam Characterization System). We first developed an image processing system to measure the sun tracking error optically. Then the measured error is modeled in linear polynomial form and neural network form trained by the extended Kalman filter respectively. Finally error models are used to compensate the sun tracking error. We also developed the necessary image processing algorithms so that the heliostat optical properties such as maximum heat flux intensity, heat flux distribution and total reflected heat energy could be analyzed. Experimentally obtained data shows that the heliostat sun tracking accuracy could be dramatically improved using either linear polynomial type error model or neural network type error model. Neural network type error model is somewhat better in improving the sun tracking performance. Nevertheless, since the difference between two error models in compensation of sun tracking error is small, a linear error model is preferred in actual implementation due to its simplicity.