• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.894-900
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• 2005

A new approach to the straightforward implementation of the unscented filter in a unit quaternion space is proposed for spacecraft attitude estimation. Since the unscented filter is formulated in a vector space and the unit quaternions do not belong to a vector space but lie on a nonlinear manifold, the weighted sum of quaternion samples does not produce a unit quaternion estimate. To overcome this difficulty, a method of weighted mean computation for quaternions is derived in rotational space, leading to a quaternion with unit norm. A quaternion multiplication is used for predicted covariance computation and quaternion update, which makes a quaternion in a filter lie in the unit quaternion space. Since the quaternion process noise increases the uncertainty in attitude orientation, modeling it either as the vector part of a quaternion or as a rotation vector is considered. Simulation results illustrate that the proposed approach successfully estimates spacecraft attitude for large initial errors and high tip-off rates, and modeling the quaternion process noise as a rotation vector is more optimal than handling it as the vector part of a quaternion.

• 한국정밀공학회지
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• 제13권6호
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• pp.161-167
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• 1996

In five-axis milling, optimal CL-data (cutter location data) should be generated to have advantages over three-axis milling in terms of accuracy and efficiency. This paper presents an algorithm for generating collision-free CL-data for five-axis milling using potential energy method. By virtually charging the cutter and part surfaces with static electricity, global collision as wells as local interference is eliminated. Additionally, machining efficiency is improved by minimizing the curvature difference between the part surface and tool swept surface at a CC-point (cutter contact point) simultaneously.

• 한국CDE학회논문집
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• 제11권6호
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• pp.422-428
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• 2006

In this paper, an NC data optimization approach for enhancing 5-axis machining speed is presented. It is usual to use expensive commercial CAD/CAM programs for NC data of 5-axis machining, since it needs very large calculations for optimal tool positioning and orientation, tool path planning, and collision-free tool path generation. Since commercial CAD/CAM systems have similar functions and efficiency based on common algorithms of reliable theories, they do not have their own unique features for machining speed and efficiency. In other words, most commercial CAD/CAM systems consider only the characteristics of part geometry to be machined, which means that they generate almost the same NC data if the part to be machined is the same, even though different machines are used for the pin. A new approach is proposed for optimizing NC data of 5-axis machining, which is based on the characteristics of the machine to be operated. As a result, the speed of 5-axis machining can increase without losing machining accuracy and surface quality.

• 한국자동차공학회논문집
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• 제25권1호
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• pp.35-41
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• 2017

The use of engineering plastics in automotive components is increasing with the trend towards improving the car strength and reducing weight. Among the different choices of materials, engineering plastic emerged as the necessary material for achieving lower costs, reduced weight and improved production efficiency. To produce the automotive parts, it is important to predict defect and validation of injection molding prior to design. Injection molding analysis and structural analysis are widely applied as a part of the design process when developing automotive parts. Injection molding analysis, in particular, involves a highly complicated mechanism that requires deep knowledge of polymer properties as well as an analytic approach different from that used for a general isotropic material when the molded material is used as a structural material. This is because the parts made of polymer have pre-stress factors such as intrinsic deformation and residual stress. The most important factors for injection molded plastic products are injection molding condition and cavity design, taking into account ease of molding, mass production and application. Despite optimal injection molding conditions and cavity design, however, glass fiber orientation is critically linked to strength reduction. The application of injection molding and structural coupled analysis provides a low-cost solution for product molding and structural validation, all prior to the actual molding. The purpose of this study involves the validation, pre-study, and solution of defect in injection-molded polymer automotive parts using the simulation software for injection molding and structural coupled analysis. Finally, this thesis provides validation of an injection molding and structural coupled analytic mechanism that can demonstrate the effect of glass fiber orientation on mechanical strength. Design improvement ideas for the injection molded product of PPS (Poly Phenylene Sulfide)+40% glass fiber are also suggested.

• International Journal of Precision Engineering and Manufacturing
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• 제2권1호
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• pp.62-75
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• 2001

The design and manufacture of injection molded polymeric parts with desired properties is a costly process dominated by empiricism including repeated modification of actual tooling. This paper presents and expert design evaluation system which can predict the mechanical performance of a molded product and diagnose the design before the actual mold is machined. The knowledge-based system synergistically combines a rule-based expert system with CAE programs. An iterative boundary pressure reflection method(IBPR) is developed to automate the cavity filling simulation program and to predict thermo-mechanical properties of a molded part precisely. Mathematical models of weldline and frozen-in molecular orientation are established to determine the spatial variation of microstructural anisotropies of a molded part from the result of cavity filling simulation. The strength ellipse is devised as and index which represents th spatial distribution of the microstructural anisotropies of a molded part, Heuristic knowledge of injection molding, flow simulation, and mechanical performance prediction is formalized as rules of an expert consultation system. The expert system interprets the analytical results of the process simulation, predicts the performance, evaluates the design and generates recommendations for optimal design alternative.

• 한국정밀공학회지
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• 제15권2호
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• pp.154-161
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• 1998

Prototypes of a design are always needed for the purpose of visualization and evaluation in the aspect of manufacturability functionality, and aesthetic appearance. Since the prototyping process requires a significant amount of cost and time, various rapid prototyping processes are recently being introduced in the process. However, it is usually necessary for a part built up by a rapid prototyping system to be refined by a post-processing process, in which the stair steps on the surfaces, the support structures (if they exist), and the unprocessed material are eliminated. This post-processing is usually done manually and is a time-consuming task. Especially, eliminating the trapped volumes, the volume of the unprocessed material entrapped by the solidified portion, is sometimes impossible in some processes. This study provides a designer with a tool to detect the existence and to calculate the quantity of the trapped volumes at the given build-up direction, so that the proper build-up direction is chosen or the part is built by pieces to avoid the problems caused by the trapped volumes in advance. Since the proposed algorithm can efficiently calculate the amount of the trapped volumes at any build-up direction, it has the potential of such application as optimizing the build-up direction to minimize the trapped volumes.

• 동력기계공학회지
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• 제17권3호
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• pp.57-64
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• 2013

This study focus on the analysis of the energy performance in accordance with apartment houses arrangement type by using Ecotect Analysis. Korea, energy-poor country, the rate of dependence on imports amount to 94%, have to reduce energy consumption part of building except in industry and transport which affect the economic. Apartment houses are built in various forms in order to reduce energy, are modelled in each window area ratio, shape, orientation, climate through simulation. Through this study, we can analyze energy performance by form, window area ratio, orientation, climate change and know the optimal elements by the form. In particular, although there have been studied research on the window area ratio and research related to the arrangement form, determined that the information on the regional climate characteristics and the direction of placement is less than existing research. To supplement those problem, adding to seven direction(West, S-60-W, S-30-W, South, S-30-E, S-60-E, East) and climatic element(southern region) is characteristic of this study. The form of apartment houses was modelled for apartment houses built in the 10 years since. And each modeling were analyzed by Ecotect Analysis.

• 동력기계공학회지
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• 제18권1호
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• pp.45-50
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• 2014

This study focuses on the analysis of the cooling and heating load in accordance with apartment houses arrangement type using Ecotect Analysis. Korea have to reduce energy consumption part of building except in industry and transport because the rate of dependence on imports amounts to 94%, Apartment houses built in various forms in order to reduce energy are modelled in each window area ratio, shape, orientation, and climate through simulation. Through this study, we can analyze the cooling and heating load by form, window area ratio, orientation, and climate change and know the optimal elements by the form. In particular, although there have been done research on the window area ratio and the arrangement form, the research of the regional climate characteristics and the direction are hardly carried out. To supplement those problem, adding to seven direction and climatic element of southern region is characteristic(L Type, Y Type, - Type) of this study. The form of apartment houses built 10 years ago is modelled for simulation.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1986년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 17-18 Oct. 1986
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• pp.431-436
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• 1986

The design and manufacture of injection molded polymeic parts with desired mechanical properties is a costly process dominated by empiricism, including the modification of actual tooling. This paper presents an interactive computer-based design system for injection molded plastic parts. This knowledge-based synthesis system provides a rational design strategy for injection molding and molded parts. It synergistically combines a rule-based expert system for hurestic knowledge with analytical process simulation programs. The theremomechanical properties of a molded part such as the effect of molecular orientation and weldline strength are predicted by the analysis programs; while the expert system interprets the analytical results from the process simulation, evaluates the design, and generates recommendations for optimal design alternatives. The heuristic knowledge of injection molding is formalized as production rules of the expert consultation system.

• 융합보안논문지
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• 제19권1호
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• pp.67-78
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• 2019

본 논문에서는 가변 크기 블록 기반의 새로운 얼굴 특징 표현 방법을 제안한다. 기존 외형 기반의 얼굴 표정 인식 방법들은 얼굴 특징을 표현하기 위해 얼굴 영상 전체를 균일한 블록으로 분할하는 uniform grid 방법을 사용하는데, 이는 다음 두가지 문제를 가지고 있다. 얼굴 이외의 배경이 포함될 수 있어 표정을 구분하는 데 방해 요소로 작용하고, 각 블록에 포함된 얼굴의 특징은 입력영상 내 얼굴의 위치, 크기 및 방위에 따라 달라질 수 있다. 본 논문에서는 이러한 문제를 해결하기 위해 유의미한 표정변화가 가장 잘 나타내는 블록의 크기와 위치를 결정하는 가변 크기 블록 방법을 제안한다. 이를 위해 얼굴의 특정점을 추출하여 표정인식에 기여도가 높은 얼굴부위에 대하여 블록 설정을 위한 기준점을 결정하고 AdaBoost 방법을 이용하여 각 얼굴부위에 대한 최적의 블록 크기를 결정하는 방법을 제시한다. 제안된 방법의 성능평가를 위해 LDTP를 이용하여 표정특징벡터를 생성하고 SVM 기반의 표정 인식 시스템을 구성하였다. 실험 결과 제안된 방법이 기존의 uniform grid 기반 방법보다 우수함을 확인하였다. 특히, 제안된 방법이 형태와 방위 등의 변화가 상대적으로 큰 MMI 데이터베이스에서 기존의 방법보다 상대적으로 우수한 성능을 보여줌으로써 입력 환경의 변화에 보다 효과적으로 적응할 수 있음을 확인하였다.