• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.91-92
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• 2008

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.3
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• pp.13-19
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• 2007

This paper described design method to minimize the crosstalk effect of multiaxis thrust measurement stand which can measure the thrust vector control performance of Solid Rocket Motor. This paper presents a theoretical solution for predicting the magnitude of crosstalk and calculates design sensitivity. The results indicate that the most important parameter of crosstalk is the displacement of flexure-loadcell-flexure assembly. And shape, dimension and mechanical properties of flexure and loadcell can also influence the magnitude of crosstalk.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.8
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• pp.904-914
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• 2011

The volumetric errors of CNC machining centers are determined by 21 errors, including 3 linear errors, 6 straightness errors, 3 perpendicular errors, 9 angular errors and non-rigid body errors of the machine tool. It is very time consuming and hard to measure all of these errors in which laser interferometer and other parts are used directly. Hence, as many as 21 separate setups and measurements are needed for the linear, straightness, angular and perpendicular errors. In case of the 5-axis machining centers, two more rotary tables are used. It can make 35 error sources of the movement. Therefore, the measured errors of multi movements of the 5-axis tables are very complicated, even if the relative measured errors are measured. This paper describes the methods, those analyze the error sources of the machining centers. Those are based on shifted diagonal measurements method (SDM), R-test and Double ball bar. In case, the angular errors of machine are small enough comparing with others, twelve errors including three linear position errors, six straightness errors and three perpendicular errors can be calculated by using SDM. To confirm the proposed method, SDM was applied to measuring 3 axes of machine tools and compared with directly measurement of each errors. In addition, the methods for measuring relative errors of multi-axis analysis methods using R-test and Double Ball Bar are introduced in this paper.

• Journal of the Korea Convergence Society
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• v.9 no.11
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• pp.277-284
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• 2018

Recently, the demand for precision machining through multi-axis machining has been greatly increased. However, it is difficult to evaluate the geometrical accuracy of the machine tool because of its complicated geometric relationship. In this study, we organized the KS/ISO specifications which are distributed in various regulations, and re-organized the geometrical precision evaluation items of multi-axis machine tools. In addition, a test workpiece was proposed to evaluate and analyze the accuracy of a multi-axis machine tool, and a test workpiece was machined according to predetermined methods and procedures, and then the machined surfaces were measured using CMM. As a result, it was verified that the machining results of the standard workpiece and the precision of the machine tool were very similar qualitatively and quantitatively. From these results, it can be confirmed that the precision analysis of the multi-axis machine tool is possible only by machining the test workpiece.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.11
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• pp.2688-2695
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• 2000

In multi-axis force sensor, compliance matrices representing structural behaviour of internal sensor bodies play an important role in decoupled sensing and accuracy, Recently, error propagation through compliance matrices has been studied via approximation approach. However the upper bound of measured force error has not been known. In this paper, error propagation in force sensing is analysed in a unified way when both strain measurement error and compliance matrix error exist, and the upper bound of the measured force error is derived exactly(not approximately). The analysis is examined through a numerical example.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.129-130
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• 2013

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.325-326
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• 2010

• Journal of the Korea Concrete Institute
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• v.16 no.2 s.80
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• pp.195-204
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• 2004

Poisson's ratio due to multiaxial creep of concrete reported by existing experimental works was controversial. Poisson's ratio calculated from measured strain is very sensitive to small experimental error. This sensitivity make it difficult to find out whether the Poisson's ratio varies with time or remain constant, and whether the Poisson's ratio has different value with stress states or not. A new approach method is needed to resolve the discrepancy and obtain reliable results. This paper presents analytical study on multiaxial creep test results. Microplane model as a new approach method is applied to optimally fitting the test data extracted from experimental studies on multiaxial creep of concrete. Double-power law is used as a model to present volumetric and deviatoric creep evolutions on a microplane. Six parameters representing the volumetric and deviatoric compliance functions are determined from regression analysis and the optimum fits accurately describe the test data. Poisson's ratio is calculated from the optimum fits and its value varies with time. Regression analysis is also performed assuming that Poisson's ratio remains constant with time. Four parameters are determined for this condition, and the error between the optimum fits and the test data is slightly larger than that for six parameter regression results. The constant Poisson's ratio with time is obtained from four parameter analysis results and the constant value can be used in practice without serious error.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.183.1-183.1
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• 2012

인공위성의 자세 제어 및 자세 결정에 사용되는 센서들의 정렬오차는 자세명령생성 오차, 자세제어 오차, 자세결정 오차 등과 더불어 지향정밀도를 저하시키는 하나의 요인으로 작용한다. 본 연구에서는 자이로 센서에만 정렬오차가 존재한다고 가정하는 상황에서 별추적기와 자이로 센서를 이용한 자세결정 필터에 의해 추정되는 자이로 바이어스 값만을 이용하여 자이로 센서의 정렬오차를 확인(Identification)하는 방법 및 결과에 대해 기술한다. 이를 추정하는 다른 방법으로는 여러 가지가 있으며 대표적으로 위성의 다축기동 정보를 입력으로 사용하는 확장칼만필터를 이용한 궤도상 보정(On-orbit Calibration) 방법이 있으나 본 연구에서는 위성의 기동 또는 많은 계산량을 소모하지 않고 비교적 간단하게 자이로 정렬오차를 추정하는 방법을 제시하였다. 그리고 실제 궤도상 위성의 거동 데이터를 이용하여 제안한 방법의 효율성을 검증하였다. 결과적으로, 제안된 방법을 이용했을 때 소수점 둘째 자리 이하의 정확도를 가지고 정렬오차가 추정됨을 확인하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.81-82
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• 2012