• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.9-14
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• 2002

Ferrule is widely used as fiber optic connecters. In fiber-optic communications, the shape accuracy such as coaxiality and cylindricity of ferrule affects insertion loss. When coaxial grinding of ferrule supported by two pin, pin alignment and chucking accuracy are very important. In this research, the kinematic behavior of the ferrule center is investigated in the case where cone-shaped center pins and round circle hales which make contact with each other near the edge of the holes, using homeogenous coordinate transformation and numerical analysis. The obtained results are as follows: The alignment errors between center pins alone do not affect the rotation accuracy of ferrule. The alignment errors between center holes cause a sinusoidal displacement of ferrule. And the maximum displacement of ferrule centers increase in proportion to the center pin angle in the case of a fixed alignment errors

• Journal of the Korean Statistical Society
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• 제33권2호
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• pp.169-189
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• 2004

Under the assumption of default priors, such as noninformative priors, Bayesian model determination and parameter estimation of regression models with stationary and invertible ARMA errors are developed under exact full likelihoods. The default Bayes factors, the fractional Bayes factor (FBF) of O'Hagan (1995) and the arithmetic intrinsic Bayes factors (AIBF) of Berger and Pericchi (1996a), are used as tools for the selection of the Bayesian model. Bayesian estimates are obtained by running the Metropolis-Hastings subchain in the Gibbs sampler. Finally, the results of numerical studies, designed to check the performance of the theoretical results discussed here, are presented.

• 로봇학회논문지
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• 제9권3호
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• pp.160-169
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• 2014

Odometry using wheel encoder is a common relative positioning technique for wheeled mobile robots. The major drawback of odometry is that the kinematic modeling errors are accumulated when the travel distance increases. Therefore, accurate calibration of odometry is required. In several related works, various schemes for odometry calibration are proposed. However, design guidelines of test tracks for odometry calibration were not considered. More accurate odometry calibration results can be achieved by using appropriate test track because the position and orientation errors after the test are affected by the test track. In this paper, we propose the design guidelines of test tracks for odometry calibration schemes using experimental heading errors. Numerical simulations and experiments clearly demonstrate that the proposed design guidelines result in more accurate calibration results.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.912-915
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• 1996

The computed-torque method (CTM) shows good trajectory tracking performance in controlling robot manipulator if there is no disturbance or modelling errors. But with the increase of a payload or the disturbance of a manipulator, the tracking errors become large. So there have been many researches to reduce the tracking error. In this paper, we propose a new control algorithm based on the CTM that decreases a tracking error by generating new reference trajectory to the controller. In this algorithm we used the concept of sliding mode theory and fuzzy system to reduce chattering in control input. For the numerical simulation, we used a 2-link robot manipulator. To simulate the disturbance due to a modelling uncertainty, we added errors to each elements of the inertia matrix and the nonlinear terms and assumed a payload to the end-effector. In this simulation, proposed method showed better trajectory tracking performance compared with the CTM.

• 대한전기학회논문지:전력기술부문A
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• 제53권7호
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• pp.375-381
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• 2004

This paper describes a three-winding transformer protective relaying algorithm based on the ratio of increments of flux linkages (RIFL). To minimize the approximation errors, the algorithm uses integration approximation. The RIFL of the two windings is equal to the turns ratio for all operating conditions except for an internal fault. For a single-phase and three-phase transformer containing the wye-connected windings, the increments of flux linkages (IFL) are calculated. For a three-phase transformer containing the delta-connected windings, the difference of IFL between the two phases are calculated to use the line currents, because the winding currents are practically unavailable. Their ratios are compared with the turns ratio. The comparative study between the proposed and differential approximation methods was conducted. The test results show that the algorithm can reduce the errors resulting from the conventional methods.

• Journal of applied mathematics & informatics
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• 제6권3호
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• pp.697-726
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• 1999

In this paper we develop a now procedure to control stepsize for linear multistep methods applied to semi-explicit index 1 differential-algebraic equations. in contrast to the standard approach the error control mechanism presented here is based on monitoring and contolling both the local and global errors of multistep formulas. As a result such methods with the local-global stepsize control solve differential-algebraic equation with any prescribed accuracy (up to round-off errors). For implicit multistep methods we give the minimum number of both full and modified Newton iterations allowing the iterative approxima-tions to be correctly used in the procedure of the local-global stepsize control. We also discuss validity of simple iterations for high accuracy solving differential-algebraic equations. Numerical tests support the the-oretical results of the paper.

• 품질경영학회지
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• 제34권2호
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• pp.12-21
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• 2006

This paper considers the problem of selecting the most profitable process mean for production processes where measurement errors exist in inspection systems. For such situations, a sequential inspection procedure is proposed to reduce measurement errors. The decision to accept, reject, or take an additional inspection of an item is made at every measurement point until the number of repeated measurements reaches its upper bound. An expected profit model is constructed and the optimal process mean, the cut-off values, and the upper bound of the number of repeated measurements are obtained when accepted(rejected) items are sold at regular(reduced) price. A numerical study is performed to investigate the performance of the proposed procedure.

• 대한기계학회논문집
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• 제12권1호
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• pp.163-172
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• 1988

본 논문에서는 GAC방법을 이용하여 공작기계의 안내면오차를 수치제어 공작기계가 가지고 있는 가공조건의 조절 능력을 이용하여 가공오차를 보상제어 함으로써 규명(identification)할 수 있는 방법을 제시한다.

• 대한기계학회논문집A
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• 제30권10호
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• pp.1249-1254
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• 2006

Existing adaptive observers may cause the parameter drifts due to disturbances even if state estimation errors remain small. To avoid the drift phenomena in the presence of bounded disturbances, several robust adaptive observers have been introduced addressing bounds in state and parameter estimates. However, it is not easy for these observers to manipulate the size of the bounds with the selection of the observer gain. In order to reduce estimation errors, this paper introduces the (equation omitted) gain minimization problem in the adaptive observer structure, which minimizes the (equation omitted) gain between disturbances and estimation errors. The stability condition of the adaptive observer is reformulated as a linear matrix inequality, and the observer gain is optimally chosen by solving the convex optimization problem. The estimation performance is demonstrated through a numerical example.

• 대한기계학회논문집
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• 제12권6호
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• pp.1312-1319
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• 1988

본 연구에서는 임의의 내접치차를 가공하기 위한 구형호브를 설계하는데 그 목적이 있으며 GTP를 구하는 방법으로는 CAD의 envelope 이론을 도입하여 근사해법이 아닌 해석적 방법으로 GTP를 구하였으며 이는 여러 오차 해석에서도 유용하게 이용되 었다.또한 호브의 설계를 위한 전산 프로그램을 개발하여 가공하고자 하는 내접치 차의 데이터로 부터 압력각, 이두께 및 피치의 값을 수정하여 호브를 설계함과 동시에 여유면 가공량을 등을 바로 계산할 수 있도록 하였으며 이에 의한 구형 호브의 설계에 를 제시하였다.