• 한국CDE학회논문집
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• 제12권3호
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• pp.153-162
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• 2007

In this paper, we propose a knowledge-based method for generating CNC torch path for laser cutting of the outlines of planar shapes. The proposed method consists of two main phases: laser cutting knowledge construction and CNC torch path generation using the knowledge. In the first phase, cutting experiments are conducted on various operating parameters, and then empirical data are stored and analyzed to make up the knowledge of laser cutting. With this knowledge, we can inquire what a kerf width is for specific operating parameters. In the second phase, using the knowledge of laser cutting, CNC torch path is generated for cutting the outlines of the given planar shapes. This phase is basically based on the offset generation of each outline by a sequence of arc splines, where the offset distance is the same as the half of the kerf width determined from the constructed knowledge. The proposed method based on laser cutting knowledge makes full use of arc interpolators in CNC torch path generation. The method can efficiently reduce the number of path segments while keeping the torch path within the desired accuracy.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.577-582
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• 2007

A variational formulation for plane elasticity problems is derived based on an isogeometric approach. The isogeometric analysis is an emerging methodology such that the basis functions in analysis domain arc generated directly from NURBS (Non-Uniform Rational B-Splines) geometry. Thus. the solution space can be represented in terms of the same functions to represent the geometry. The coefficients of basis functions or the control variables play the role of degrees-of-freedom. Furthermore, due to h-. p-, and k-refinement schemes, the high order geometric features can be described exactly and easily without tedious re-meshing process. The isogeometric sensitivity analysis method enables us to analyze arbitrarily shaped structures without re-meshing. Also, it provides a precise construction method of finite element model to exactly represent geometry using B-spline base functions in CAD geometric modeling. To obtain precise shape sensitivity, the normal and curvature of boundary should be taken into account in the shape sensitivity expressions. However, in conventional finite element methods, the normal information is inaccurate and the curvature is generally missing due to the use of linear interpolation functions. A continuum-based adjoint sensitivity analysis method using the isogeometric approach is derived for the plane elasticity problems. The conventional shape optimization using the finite element method has some difficulties in the parameterization of boundary. In isogeometric analysis, however, the geometric properties arc already embedded in the B-spline shape functions and control points. The perturbation of control points in isogeometric analysis automatically results in shape changes. Using the conventional finite clement method, the inter-element continuity of the design space is not guaranteed so that the normal vector and curvature arc not accurate enough. On tile other hand, in isogeometric analysis, these values arc continuous over the whole design space so that accurate shape sensitivity can be obtained. Through numerical examples, the developed isogeometric sensitivity analysis method is verified to show excellent agreement with finite difference sensitivity.

• 대한공간정보학회지
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• 제17권3호
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• pp.115-120
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• 2009

기존의 도화사 수작업에 의한 기준점기반 항공삼각측량 기법은 전통적인 사진측량에서 유용하게 이용되어 왔으나, 자동화된 수치사진측량 기법이 확산되면서 기존방법의 문제점이 대두되었다. 따라서 본 논문은 보다 발전된 자동화 기술 개발을 위하여 상위 레벨인 선형객체들을 이용한 항공삼각측량 가능성을 제시하고 검증하고자 하였다. 최근에 발달된 선형 객체 추출기법 알고리즘은 보다 정확한 선형 객체 추출기법을 제공하였지만, 포인트 추출기법에 비하여 추출하기 어려운 단점이 존재한다. 따라서 본 논문은 이를 극복하기 위하여 수동 디지타이징이나 에지 연산자를 통하여 쉽게 획득되는 포인트를 이용하여 상위레벨 선형객체를 생성하고, 이를 통해 지형공간정보 이용 가능성을 높이고자 하였다. 본 연구 결과를 통해 진화하고 있는 컴퓨터 환경에 적합한 선형객체를 이용한 항공삼각측량 기법을 발전시킬 것으로 기대된다.

• 한국정밀공학회지
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• 제14권11호
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• pp.77-83
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• 1997

This work is concerned with the algorithm of generating a new circular are interpolation. This research presents a new biarc curve fitting that is a circular interpolation method based on a triarc curve fitting. The triarc method, where a segment span is composed of three circular arcs, using maximum error estimation has the advantage of generating arc splines easily to a given tolerance. The new biarc method is called when the adjacent radii are the same in the same in the triarc method. In generating the machining data for various cam curves in CNC machining with the biarc method and the new biarc method, the latter accomp- lished faster NC-code generation, shorter NC-code block formation and machined the same cam profile more efficiently.