• Nuclear Engineering and Technology
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• 제53권8호
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• pp.2708-2715
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• 2021

The Multi-Purpose Overload Robot (CMOR) is a key subsystem of China Fusion Engineering Test Reactor (CFETR) remote handling system. Due to the long cantilever and large loads of the CMOR, it has a large rigid-flexible coupling deformation that results in a poor position accuracy of the end-effector. In this study, based on the Levenberg-Marquardt algorithm, the spatial grid, and the linearized variable load principle, a variable parameter compensation model was designed to identify the parameters of the CMOR's kinematics models under different loads and at different poses so as to improve the trajectory tracking accuracy. Finally, through Adams-MATLAB/Simulink, the trajectory tracking accuracy of the CMOR's rigid-flexible coupling model was analyzed, and the end position error exceeded 0.1 m. After the variable parameter compensation model, the average position error of the end-effector became less than 0.02 m, which provides a reference for CMOR error compensation.

• 대한기계학회논문집A
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• 제30권8호
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• pp.957-964
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• 2006

As the requirement of LCD products which are large screen and have high brightness increases, the role of light guide panel (LGP) of which micro-features diffuse the light uniformly on surface is getting important. In general, there are many errors in machining like machine tool errors process error, setup error and etc. The amount of setup error in general machining is not so big in comparison with the others, so it is mostly neglected. But, especially in v-groove micromachining, setup error has a significant effect on micro-features. Low quality product and high cost are resulted from setup error. In v-groove micromachining, to confirm the effect of setup error, it is identified and then setup error synthesis model is derived from analysis of tool and workpiece setup. In addition, to predict the micro-features affected by setup error and enhance the production efficiency, the setup condition satisfying the tolerance of micro-features is geometrically analyzed and presented.

• Communications for Statistical Applications and Methods
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• 제10권2호
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• pp.553-566
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• 2003

In many cases, the measurement error variances may be functions of the unknown true values or related covariates. This paper considers design-based estimators of the parameters of these variance functions based on the within-unit sample variances. This paper devotes to: (1) define an error scale factor $\delta$; (2) develop estimators of the parameters of the linear measurement error variance function of the true values under large-sample and small-error conditions; (3) use propensity methods to adjust survey weights to account for possible selection effects at the replicate level. The proposed methods are applied to medical examination data from the U.S. Third National Health and Nutrition Examination Survey (NHANES III).

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1993년도 추계학술대회 논문집
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• pp.527-532
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• 1993

MascMC system is one of the MMC system module which performs measuring and checking of machined workpieces on the machine tools. Accuracy of the MascMC was compensated for developing a reliable measuring system by measurement error calibration. Reference gauges, ring gauges, block gauges,squares, spheres and cylindrical squares, were used for error identification and compensation. .+-. 10 .mu. m accuracy with 95% confidence interval was confirmed on the vertical and the horizontal machining center through the large number of experiments.

• 한국기계가공학회지
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• 제6권4호
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• pp.57-64
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• 2007

In the recent years, development of machine tool with high speed feeding system have brought a rapid increase in productivity. Practically, thermal deformation problem due to high speed is, however, become a large obstacle to realize high precision machining. In this study, therefore, the construction of automatic error compensation system to control thermal deformation in high speed feeding system with real time is proposed. To attain this purpose, high speed feeding system with feeding speed 60mm/min is developed and experimental equation for relationship between thermal deformation and temperature of ball screw shaft using multiple regression analysis is established. Furthermore, in order to analyze thermal deformation error, compensation coefficient is determined and thermal deformation experiments is carried out. From obtained results, it is confirmed that automatic error compensation system constructed in this study is able to control thermal deformation error within $15{\sim}20{\mu}m$.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.964-967
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• 2001

Aspherical lens with the higher numerical aperture has been needed in the optical storage device to increase the recording density on the disk. However, high numerical aperture means the large slope angle at the clear aperture of the lens. Therefore, the measurement and manufacturing technique including the lens molding process for the slope angle should be developed. In this paper, the evaluation technique was described for the optical performance of the aspherical lens. Aspherical form error brings about the wavefront error and the side lobe of the beam intensity profile. A schematic diagram of the aspherical lens manufacturing was drawn to explain the aspherical form error compensation. Finally, form error of the aspherical lens was defined and plotted using the raw data of the Formtalysurf.

• 한국정밀공학회지
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• 제28권2호
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• pp.168-175
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• 2011

Contouring accuracy of CNC machine tools is very important for high-speed and high-precision machining. In particular, large contour error may occur during corner tracking. In order to reduce the corner contouring error, acceleration and deceleration control or tool-path planning methods have been suggested. However, they do not directly control the corner contouring error. In the meantime, network servo systems are widely used because of their easiness of building and cost effectiveness. Communication latency between the master controller and servo drives, however, may deteriorate contouring accuracy especially during corner tracking. This paper proposes a control strategy that can accurately calculate and directly control the corner contouring error. A prediction control is combined with the above control to cope with communication latency. The proposed control method is evaluated through computer simulation and experiments. The results show its validity and usefulness.

• 한국광학회지
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• 제28권6호
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• pp.281-289
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• 2017

본 연구에서는 한국표준과학연구원(KRISS)에 설치된 대구경 반사경용 광학측정타워를 이용한 광학측정 시 타워에 유입되는 진동과 그로 인해 발생하는 광학측정오차에 대한 분석을 수행하였다. 여러 환경조건에 대해 타워구조물, 간섭계, Null lens의 진동측정을 수행하였으며 동시에 직경 600 mm의 축대칭 비구면 반사경의 광학측정을 수행하여 진동과 광학측정오차간의 연관성을 분석하였다. 진동측정 결과 타워의 상단에 위치한 Null lens 및 간섭계가 외부 진동요인에 매우 취약하여 외부 진동유입 시 광학측정오차가 민감하게 증가됨을 확인할 수 있었다. 특히 간섭계와 Null lens의 각 방향 진동이 서로 다르게 발생하는 경우 광학측정오차가 크게 증가하는 것으로 나타났다. 진동에 의한 간섭계, Null lens, 반사경의 정렬오차를 줄이기 위해 타워 구조 시스템이 저주파 진동에 둔감하도록 구조개선이 필요할 것으로 판단되며 진동 모니터링을 통해 간섭계와 Null lens의 진동이 안정화된 시점에 광학측정을 수행하여야 형상 오차 측정값에 대한 신뢰도를 높일 수 있는 것이라 사료된다.

• Journal of Positioning, Navigation, and Timing
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• 제5권1호
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• pp.1-9
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• 2016

Range-based wireless localization system must measure accurate range between a mobile node (MN) and reference nodes. However, non-line-of-sight (NLOS) error caused by the spatial structures disturbs the localization system obtaining the accurate range measurements. Localization methods using the range measurements including NLOS error yield large localization error. But filter-based localization methods can provide comparatively accurate location solution. Motivated by the accuracy of the filter-based localization method, a filter residual-based NLOS error estimation method is presented in this paper. Range measurement-based residual contains NLOS error. By considering this factor with NLOS error properties, NLOS error is mitigated. Also a process noise covariance matrix tuning method is presented to reduce the time-delay estimation error caused by the single dynamic model-based filter when the speed or moving direction of a MN changes, that is the used dynamic model is not fit the current dynamic of a MN. The presented methods are evaluated by simulation allowing direct comparison between different localization methods. The simulation results show that the presented filter is more accurate than the iterative least squares- and extended Kalman filter-based localization methods.

• 한국융합학회논문지
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• 제8권5호
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• pp.185-192
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• 2017

공작기계의 오차는 크게 기하하적 오차, 열변형 오차 및 가공오차로 나눌 수 있다. 본 연구에서는 2차원 가공에서, 각 오차의 원인이 전체 오차에 미치는 영향과 각 오차의 상대적 크기를 정량적으로 분석하였다. 오차의 상대적 크기는 열변형 오차와 가공오차가 상대적으로 기하학적 오차에 비해 크게 나타났으며, 이는 가공 정밀도에 직접적으로 관계된다고 판단되었다. 세 가지 오차를 제거하기 위해 측정된 오차 프로파일을 이용하여 오차의 보정가능성을 검토하였다. 그 결과 각각의 오차요인에 대하여 약 50%의 시스템 오차를 보정할 수 있었으며, 특히, 열변형 오차와 가공오차의 경우 큰 폭으로 오차를 보정할 수 있음을 확인하였다. 본 연구를 통하여 가공에 관한 기본적인 데이터 베이스를 구축할 수 있으며, 이를 통해 사용자 관점에서 가공오차에 대한 보정이 가능할 것으로 기대된다.