• Journal of the Korean Society for Precision Engineering
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• v.15 no.11
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• pp.67-75
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• 1998

Geometric and thermal errors are key contributors to the errors of a computer numerically controlled turning center. A planar error synthesis model is obtained by synthesizing 11 geometric and thermal error components of a turning center with homogeneous coordinate transformation method. This paper shows the sensitivity analysis on the temperature change, the confidence evaluation on the uncertainty Of measurement systems, and the error contribution analysis from the planar error synthesis model. Planar error in the z direction was very sensitive to the temperature change. and planar errors in the x and z directions were not affected by the uncertainty of measurement systems. The error contribution analysis ,which is applicable to designing a new turning center, was helpful to find the large error components which affect planar errors of the turning center.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.3
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• pp.187-193
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• 2003

This paper presents an on-machine measurement method of flatness error fur surface machining processes. There are two kinds of on-machine measurement methods available to measure flatness errors in workpieces: i.e., surface scanning method and sensor scanning method. However, motion errors are often engaged in both methods. This paper proposes an idea to realize a measurement system of flatness errors and its rigorous application for estimation of motion errors of the positioning system. The measurement system is made by modifying the straightness measurement system, which consists of a laser, a CCD camera and processing system, a sensor head, and some optical units. The sensor head is composed of a retroreflector, a ball and ball socket, a linear motion guide unit and adjustable arms. The experimental .results show that the proposed method is useful to identify flatness errors of machined workpieces as well as motion errors of positioning systems.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.11a
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• pp.482-485
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• 2012

본 논문은 평면 디스플레이 패널 외관 검사의 무인 자동화를 위한 전처리 단계의 알고리즘으로 패널 외관 검사 영역의 정합성 향상 및 자동 설정하는 알고리즘 기술에 관한 것이다. 평면디스플레이 패널의 제조 공정 중, 점등 검사 공정 단계에서는 Line 불량, Point 불량, 얼룩 불량, 외관 불량, Pol 불량 등 다양한 불량들을 검출한다. 이중 외관 불량 검사를 자동화하기 위한 전처리 단계로써 획득한 영상 내에서의 검사 영역을 설정함에 있어서 영상에서의 패널 위치의 변화, 패널의 Rotation/tilt, 패널 에지에 불량이 결부될 경우에도 실제 절단면을 정확하게 추출하여 불량 측정 오차를 최소화하는 알고리즘 을 제안한다.

• Journal of the Korean Institute of Intelligent Systems
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• v.12 no.6
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• pp.524-530
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• 2002

This note suggests a stepwise fuzzy moving sliding surface using Sugeno-type fuzzy system and presents a sliding mode control scheme using it. The fuzzy system has the angle of state error vector and the distance from the origin in the phase plane as inputs and a first-order linear differential equation as output. The surface initially passes arbitrary initial states and subsequently moves towards a predetermined surface via rotating or shifting. This method reduces the reaching and tracking time and improves robustness. Conceptually the slope of the Proposed fuzzy moving sliding surface increases stepwise in the stable region of the phase plane. The surface, however, rotates continuously because the surface is a fuzzy system. The asymptotic stability of the fuzzy sliding surface is proved. The validity of the proposed control scheme is shown in computer simulation for a second-order nonlinear system.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.1
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• pp.1-10
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• 2004

Adaptive finite element analysis, in which its solution error meets with the user defined allowable error, is recently used to improve the reliability of finite element analysis results. This adaptive analysis is composed of two procedures; one is the error estimation of an analysis result and the other is the reconstruction of finite elements. In the (p-method, an element size is controlled by relocating of nodal positions (r-method) and the order of an element shape function is determined by the hierarchical polynomial (p-method) corresponding to the clement solution error by the enhanced SPR. In order to show the effectiveness and the accuracy of the suggested rp-method, various numerical examples were analyzed and these analysis results were examined by comparing with those obtained by the existed methods.

• Journal of KIISE:Software and Applications
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• v.27 no.4
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• pp.422-431
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• 2000

This paper proposes a new codebook generation method, called a PCA-Based VQ, that incorporates the PCA (Principal Component Analysis) technique into VQ (Vector Quantization) codebook design. The PCA technique reduces the data dimensions by transforming input image vectors into the feature vectors. The cluster of feature vectors in the transformed domain is bisectioned into two subclusters by an optimally chosen partitioning hyperplane. We expedite the searching of the optimal partitioning hyperplane that is the most time consuming process by considering that (1) the optimal partitioning hyperplane is perpendicular to the first principal axis of the feature vectors, (2) it is located on the equilibrium point of the left and right cluster's distortions, and (3) the left and right cluster's distortions can be adjusted incrementally. This principal axis bisectioning is successively performed on the cluster whose difference of distortion between before and after bisection is the maximum among the existing clusters until the total distortion of clusters becomes as small as the desired level. Simulation results show that the proposed PCA-based VQ method is promising because its reconstruction performance is as good as that of the SOFM (Self-Organizing Feature Maps) method and its codebook generation is as fast as that of the K-means method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.12C
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• pp.1214-1221
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• 2005

In this paper, we propose a digital watermarking method for still images, in which the human visual system (HVS) is used in the discrete cosine transform (DCT) domain. The modulation transfer function (MTF) of the HVS model is employed to increase the invisibility of the inserted watermark in images. The proposed watermarking method is shown to be robust to several common image processing techniques, including lowpass filtering and cropping. Also, using the energy relationship of the DCT, we derive the equation that directly computes the watermark weighting factor in the DCT domain for the specified peak signal to noise ratio (PSNR) of the still image and the length of watermark to be inserted. The difference between desired PSNR and PSNR in spatial domain is within 0.07dB for the 7 test images.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.04a
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• pp.120-124
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• 1992

평면 연삭가공에 있어서 피삭재의 진직도의 제어는 정밀계측기와 같은 정밀기기의 제작에 중요한 문재중 하나이다. 본 연구에서는 연삭작업 능률을 향상시키기 위해 고 능률 단공정 가공시 발생할 수 있는 피삭재의 열변형기등을 유한요소법으로 밝힌것을 기초로 실험과의 타당성 여부를 검토하고, 고능률 연삭시 형상오차에 미치는 여러가지인자의 영향을 조사하였으며, 회귀분석에의해 형상오차의 추정치를 예측하였다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.15 no.1
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• pp.1-7
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• 1997

In the digital mapping for data base contruction, the positional information is used as an important tool in LIS/GIS(Land Information System/Geographic Information System) that is used for a facility management, urban/cadastral management as well as in spatial analysis. In this paper, for an error analysis of X, Y coordinates data on digital map, test area was classified by topography, density, and slope. The coordinates on topographic map were assumed as true values and they were compared with the coordinates on digital map. A result of the numerical test show that a vector data of line type had more gross error than vector data of polygon type. And, SME(stanadrd mean error) of urban or intermountain area had small values compared to that of suburban area in topography analysis. The SME of dense and middle zone had small values compared to that of loose zone in density analysis. In another slope analysis. the SME of steep of gentle slope had small values compared to that of flatland.

• The Journal of the Acoustical Society of Korea
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• v.20 no.6
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• pp.75-81
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• 2001

In this paper we analyzed the localization error of near-field detection algorithm in the sea. The near-field detection algorithms using triangulation and wavefront curvature basically assume a signal in two dimension of bearing and range. But the assumption causes localization error because there is three dimension of bearing, range, and depth in the sea. Even through three dimensional effect is considered, the localization error is occurred if multipath propagation in the sea is ignored. To analyze the localization error in the sea, we simulate the near-field localization using acoustic propagation model and focused beamforming considering wavefront curvature. The simulation results indicate that localization error always occurs in the sea and the error varied with sound velocity profile, water depth, bottom slope, source range, etc.