• 제목/요약/키워드: Curve fairing

검색결과 11건 처리시간 0.015초

3D NURBS 곡선의 해석적 및 이산적 순정 (Analytic and Discrete Fairing of 3D NURBS Curves)

  • 홍충성;홍석용;이현찬
    • 한국CDE학회논문집
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    • 제4권2호
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    • pp.127-138
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    • 1999
  • For reverse engineering, curves and surfaces are modeled for new products by interpolating the digitized data points. But there are many measuring or deviation errors. Therefore, it is important to handle errors during the curve or surface modeling. If the errors are ignored, designer could get undesirable results. For this reason, fairing procedure with the aesthetics criteria is necessary in computer modeling. This paper presents methods of 3D NURBS curve fairing. The techniques are based on automatic repositioning of the digitized dat points or the NURBS curve control points by a constrained nonlinear optimization algorithm. The objective function is derived variously by derived curved. Constraints are distance measures between the original and the modified digitized data points. Changes I curve shape are analyzed by illustrations of curve shapes, and continuous plotting of curvature and torsion.

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개선된 직접 곡률 조작법을 이용한 선형의 순정 (Hull Fairing by Modified Direct Curvature Manipulation Method)

  • 윤태경;김동준
    • 한국해양공학회지
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    • 제13권4호통권35호
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    • pp.169-173
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    • 1999
  • In this paper some modifications for Lu's inverse method of fairing process are presented. The object function is changed and additional constraints for hull curve foiling is proposed. The newly introduced minimizing object function is the sum of the distances between the two curve's positions at the same parameter values instead of the sum of the distances between two vertices. The new one is better to represent the physical meaning of the object function, the smaller differences between two curves. In ship hull fairing the end tangent of curve has to be fined in some cases, so the additional constraint is considered to preserve the direction of end tangent. The sample results are shown.

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선형의 자동순정 및 모델링 시스템에 관한 연구 (A Study on the Automatic Fairing and Modeling System of Hull From)

  • 김동준
    • 한국해양공학회지
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    • 제14권2호
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    • pp.121-127
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    • 2000
  • In this paper a new technique of inverse fairing problem for ship hull is proposed. Recently Lu solved the inverse fairing problem for automobile's body that was made by one surface element. In this system however hull surface is constructed by Gregory's composite surface interpolation method. So reflection line at boundary position is used as a tool of solving inverse problem in surface fairing. But the results are not good. The new concepts of Normal vector line and Constrained reflection line are introduced as an alternative tool. Energy minimization method for Normal Vector Line curve net and the inverse method for Constrained Reflection Line by using optimization technique are examined And the final lines from this proposed surface fairing method shows good fairness.

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다항식회귀곡선을 통한 임펠러의 역공학 적용에 관한 연구 (A Study on the Application of Reverse Engineering for Impeller using Polynomial Regression)

  • 황종대;정종윤;정윤교
    • 한국공작기계학회논문집
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    • 제13권5호
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    • pp.103-109
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    • 2004
  • This paper presents a fairing method for reverse engineering of a free-formed surface. Utilizing measured data points, reverse engineering is a useful method to construct a CAD model from physical model. Measured data points should be faired since raw data may have outliers. A fairing algorithm of polynomial regression model generates smooth curves of approximation in this paper. The faired curves are utilized to construct a free-formed surface. For a verifying example, an impeller blade is digitized with a CMM to collect raw data on the surfacce and a CAD model is constructed. This research produces impeller blades with 5-axis machining center through the CAD model and compares them with a physical model. As a result the produced surface modeled with the fairing method gives less error than that without the fairing.

CAD for styling design

  • Park, Sehyung;Lee, Chong-won;Kim, Jin-oh
    • 제어로봇시스템학회:학술대회논문집
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    • 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집(한일합동학술편); 한국과학기술대학, 충남; 16-17 Oct. 1987
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    • pp.780-785
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    • 1987
  • The measuring point data of clay model are widely used to design parts whose external features are important design factor such as automobiles and general die products. This paper presents a method for improving the process to generate smooth surfaces from the measuring point data using turnkey CAD/CAM system. The process of smooth-surface generation involves several steps: styline finding, curve fairing, surface generation and filleting. The process is improved by automatic curve fairing, local correction of surface and multi-boundary surface treatment. An automobile bumper and a telephone receiver are measured and modeled to test the new method. Significant time saving is resulted by changing interactive mode to automatic mode and eliminating inefficient loop of surface generation process.

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가상 측정을 통한 펜슬곡선 추출 (Pencil Curve Tracing via Virtual Digitizing)

  • 박정환;김보현;최병규
    • 한국CDE학회논문집
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    • 제2권4호
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    • pp.253-266
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    • 1997
  • Pencil-curve machining, which is a single-pass ball-end milling along a concave edge on adie surface, is widely employed in die-surface machining. The cutter-path used for pencil-curve machining, which is the trajectory of the “ball-center point” of a ball-endmill sliding along a concave-edge region on the die surface, is called pencil-curve. Presented in the paper is a pencil-curve tracing algorithm in which “concave-type” sharp edges are computed from a “virtually digitized” model of the tool-envelope surface. The resulting “initial” pencil-cures are then refuted by applying a series of fairing operations. illustrative examples and methods for enhancing accuracy are also presented. The proposed pencil-curve tracing algorithm has been successfully implemented in a commercial CAM system specialized in die-machining and in the CAD/CAM system CATIA.

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선형의 순정 기법에 관한 기초 연구 (A Basic Study on the Fairing Method of Ship Hull Surface)

  • 김동준;윤태경
    • 대한조선학회논문집
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    • 제31권2호
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    • pp.15-21
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    • 1994
  • 전산기를 이용한 순정작업은 크게 두 가지로 구분할 수 있다. 첫번째는 단면곡선, 즉 2차원 곡선을 순정하고 다른 단면에서도 역시 부드러운가를 확인하는 전통적인 방법이다. 두번째는 곡면을 이용하는 것으로 전산기의 발달과 더불어 최근 많이 사용하고 있는 방법이다. 그러나 이 경우 먼저 선형을 곡면으로 정의하여야 하나 복잡한 선형의 경우 쉽지가 않다. 본 연구에서는 곡선의 순정기법을 확장하여 그물망 곡선(mesh curve)의 경우에 대해 비균일(non-uniform) B-Sp line 곡선을 이용한 Rong의 방법으로 선형의 순정작업을 행하였다. 그러나 Rong의 방법에는 곡선의 양 끝점에서의 기울기가 고정되어야 하는 제한이 있으며 곡면화 방법에 대한 기술이 명확하지 못하다. 본 연구에서는 곡선의 양끝의 기울기를 고정시키지 않고 순정작업을 할 수 있도록 하였으며, 순정된 결과를 곡면화하는 방법을 제안하였다.

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[$GC^1$] 곡면을 이용한 선형의 표현 (Definition of Ship Hull using $GC^1$ Surface)

  • 박지선;김동준
    • 대한조선학회논문집
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    • 제31권4호
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    • pp.32-40
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    • 1994
  • 선박설계에 있어 초기선형설계는 설계요구를 만족하는 초기선형 정의와 정의된 선형의 순정 과정을 거친다. 이 과정에서 선형의 3차원적 정의와 효과적인 순정방법이 동시에 요구된다. 본 논문에서는 곡선망 선형순정법의 결과로 얻어지는 곡선망 선형을 이용하여 곡면간 기하학적 연속($GC^1$)이 만족되는 곡면으로 선형을 정의하였다. 본 논문에서 제시된 방법은 곡선망의 생성과정에서 나타날 수 있는 불규칙한 다각형에 대해서도 곡면화가 가능한 방법이다. Hermite 혼합 Coons 면조각, Convex 조합, Gregory 면조각 보간방법을 선형곡면화에 적용시켜 선체를 3차원 곡면으로 표현했다. 생성된 곡면의 순정도에 대한 검증은 곡면간 교차를 통한 수치적인 방법을 적용하였으며, 실선에 작용한 결과를 예로서 보였다.

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활주형 선박의 선형설계를 위한 통합 CAD/CAE 시스템 (Integrated CAD/CAE System for Planing Hull Form Design)

  • 김태윤;김동준
    • 수산해양기술연구
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    • 제39권4호
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    • pp.298-304
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    • 2003
  • In this paper a free-form hull design program and performance prediction program for planing boat is introduced. This program enables the designer to do complex geometric hull shape design on a personal computer and accurately to predict power requirements for a given loading and velocity. For a free form design, Bezier curve model is adopted as a basic representation tool of curves and surfaces, and this program has versatile functions to do fairing jobs with a convenient graphical user interface. After creating a hull form the geometric data is provided in a manner compatible with a variety of analysis tools including 'Motion Analysis(by Zarnick)' for prediction of motion characteristics in regular waves, 'Running Attitude (by Savitsky)' for prediction of the running attitude and required power.

혼합 곡선 근사법을 이용한 선형 표현 (Hull Form Representation using a Hybrid Curve Approximation)

  • 김현철;이경선;김수영
    • 대한조선학회논문집
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    • 제35권4호
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    • pp.118-125
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    • 1998
  • 본 연구는 B-spline 근사법과 유전자 알고리즘을 이용하여 기하학적 경계 조건-양끝점의 위치 벡터 및 접선 벡터-을 만족하는 혼합 곡선 근사법에 의한 선형 표현을 내용으로 한다. B-spline 근사법을 이용하여 선형을 표현하고, 이들 곡선을 제어하는 조정점들이 기하학적 경계조건을 만족하도록 유전자 알고리즘으로 조정한다. 이 방법은 선형 생성시 순정 작업을 동시에 수행하므로 효율적인 선형 설계를 가능하게 한다.

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