检索结果-内蒙古大学图书馆

作者： Barhak, J. Fischer, A. CMSR Laboratory for Computer Graphics and CAD Department of Mechanical Engineering Technion-Israel Institute of Technology Haifa Israel

There are several open problems that are viewed as a bottleneck in the reverse engineering process: (1) The topology is unknown;therefore, point connectivity relations are undefined. (2) The fitted surface must satisfy global and local shape preservation criteria, which are undefined explicitly. The reconstruction is based on parameterization and fitting stages. However, the above problems are influenced mainly by the parameterization. To overcome the above problems, the neural network self-organizing map (SOM) method is proposed for creating a 3D parametric grid. The main advantage of the SOM method is that it detects the orientation of the grid and the position of the sub-boundaries. Then through an adaptive process the neural network grid is converged to the sampled shape. The SOM method is applied directly on a 3D grid and avoids projection anomalies, which are common to other methods. For the surface fitting stage the random surface error correction fitting method, which is based on the SOM method, was developed and implemented. © 2002 Elsevier Science Ltd. All rights reserved.

关键词： Reverse engineering

来源：评论

学校读者我要写书评

暂无评论

Adaptive parameterization for reconstruction of 3D freeform objects from laser-scanned data 7

Adaptive parameterization for reconstruction of 3D freeform ...

引用

7th Pacific Conference on computer graphics and Applications, Pacific graphics 1999

作者： Fischer, A. Manor, A. Barhak, Y. CMSR Laboratory for Computer Graphics and CAD Department of Mechanical Engineering Technion - Israel Institute of Technology Haifa32000 Israel

ISBN: (纸本)0769502938

This paper proposes a new adaptive parametrization method to overcome the problems of using laser scanners in Reverse engineering. The method is based on the following stages: (a) Detecting a 3D boundary of the parametric base surface by matching an intensity image from a CCD camera with the scanned data. (b) Adaptively reconstructing a parametric base surface with a non-self intersecting grid, based on a PDE method (c) Calculating the parametrization of the 3D sampled points. (d) Fitting the surface by applying a least square (LSQ) approximation method with boundary constraints. The feasibility of the parametrization algorithm is demonstrated on several examples using sculptured free objects. © 1999 IEEE.

关键词： Reverse engineering

来源：评论

学校读者我要写书评

暂无评论

Verification of scanned engineering parts with cad models based on discrete curvature estimation

Verification of scanned engineering parts with CAD models ba...

引用

作者： Lipshitz, B. Fischer, A. Laboratory for Computer Graphics and CAD Department of Mechanical Engineering Technion-Israel Institute of Technology Haifa Israel

The manufacturing industry constantly needs to verify machined objects against their original cad models. Given a prototype design, an engineer should be able to determine whether the part was manufactured well;that is, whether it fits the cad model exactly. However, derivative computations are unstable for real data, and the estimated curvature is thus very sensitive to noise. Moreover, in many cases, spatial fitting of corresponding points is not sufficient. The current work utilizes the curvature properties to inspect manufactured parts that have been reconstructed from noisy and densely sampled data. Copyright © 2005 by ASME.

关键词： computer aided design

来源：评论

学校读者我要写书评

暂无评论

CNC interpolators: algorithms and analysis

CNC interpolators: algorithms and analysis

引用

Proceedings of the 1993 ASME Winter Annual Meeting

作者： Koren, Y. Lo, C.C. Shpitalni, M. Department of Mechanical Engineering University of Michigan Ann Arbor MI United States Laboratory for Computer Graphics and CAD Faculty of Mechanical Engineering Technion Haifa Israel

ISBN: (纸本)0791810291

cad systems today interpolate general curves by dividing each curve into many straight-line segments which are downloaded to the CNC. Determining the number of lines to be transferred from the cad to the CNC poses a conflict between the desired precision of the part and the feedrate fidelity. The current method results in severe variations in the feedrate, leading, in turn, to variations in the surface smoothness and a substantial increase in machining time. These problems are caused by the acceleration/deceleration at the ends of each segment. Moreover, the problems are inherent in the CNC interpolator, as is thoroughly discussed in this paper. These problems can be solved by the development of curve interpolation algorithms for CNC. In this paper, a real-time interpolation algorithm for curves presented in their parametric forms is proposed and compared with the existing cad interpolators. Analysis shows that with this new interpolator, a constant feed is maintained along the cut and the machining time is as expected. In addition, the amount of geometric information transferred from the cad system to the CNC is reduced by orders of magnitude. Moreover, the contour errors caused by the new interpolator are much smaller than those caused by conventional cad interpolators.

关键词： Numerical control systems

来源：评论

学校读者我要写书评

暂无评论

Adaptive reconstruction of freeform objects with 3D SOM neural network grids

Adaptive reconstruction of freeform objects with 3D SOM neur...

引用

Pacific Conference on computer graphics and Applications

作者： J. Barhak A. Fischer CMSR Laboratory for Computer Graphics and CAD Department of Mechanical Engineering Technion-Israel Institute of Technology Haifa Israel

Reverse engineering is an important process in cad systems today. Yet several open problems lead to a bottleneck in the reverse engineering process. First, because the topology of the object to be reconstructed is unknown, point connectivity relations are undefined. Second, the fitted surface must satisfy global and local shape preservation criteria that are undefined explicitly. In reverse engineering, object reconstruction is based both on parameterization and on fitting. Nevertheless, the above problems are influenced mainly by parameterization. In order to overcome the above problems, the paper proposes a neural network, Self Organizing Map (SOM) method, for creating a 3D parametric grid. The main advantage of the proposed SOM method is that it detects both the orientation of the grid and the position of the sub-boundaries. The neural network grid converges to the sampled shape through an adaptive learning process. The SOM method is applied directly on 3D sampled data and avoids the projection anomalies common to other methods. The paper also presents boundary correction and growing grid extensions to the SOM method. In the surface fitting stage, an RSEC (Random Surface Error Correction) fitting method based on the SOM method was developed and implemented.

关键词： Neural networks Surface fitting Reverse engineering Surface reconstruction Shape Spline Laser modes Data mining Jacobian matrices Laboratories

来源：评论

学校读者我要写书评

暂无评论

Topology recognition of 3D closed freeform objects based on topological graphs

Topology recognition of 3D closed freeform objects based on ...

引用

Pacific Conference on computer graphics and Applications

作者： D. Steiner A. Fischer CMSR Laboratory for Computer Graphics and CAD Department of Mechanical Engineering Technion-Israel Institute of Technology Haifa Israel

ISBN: (纸本)0769512275

Reverse engineering (RE) deals with an enormous number of irregular and scattered digitized points that require intensive processing in order to reconstruct the surfaces of an object. Surface reconstruction of freeform objects is based on geometrical and topological criteria. Current fitting methods reconstruct an object using a bottom-up approach, from points to a dense mesh, and finally into smoothed connected freeform sub-surfaces. This type of reconstruction, however, can cause topological problems that lead to undesired surface fitting results. Such problems are particularly common with concave shapes. To avoid problems of this type, the paper proposes a new method that automatically detects the topological structure of an object as a base for surface fitting. The topological reconstruction method described in the paper is based on two stages: (1) creating 3D non-self-intersecting iso-curves from a 3D triangular mesh and (2) extracting a topological graph. The feasibility of the proposed topological reconstruction method is demonstrated on several examples using freeform objects with complex topologies.

关键词： Topology Surface fitting Surface reconstruction Shape Reconstruction algorithms Reverse engineering Laboratories computer graphics mechanical engineering Scattering

来源：评论

学校读者我要写书评

暂无评论

Surface Reconstruction of Freeform Objects Based on Multiresolution Volumetric Method

引用

Journal of Computing and Information Science in engineering 2003年第4期3卷 334-338页

作者： Azernikov , Sergei Miropolsky , Alex Fischer , Anath Laboratory for Computer Graphics and CAD Department of Mechanical Engineering Technion–Israel Institute of Technology Haifa Israel 32000

Recently developed 3D scanning devices are capable of capturing point clouds, as well as additional information, such as normals and texture. This paper describes a new and fast reverse engineering method for creating a 3D computerized model from data captured by such contemporary 3D scanning devices. The proposed method aggregates large-scale 3D scanned data into an extended Hierarchical Space Decomposition Model (HSDM) based on Octree data structure. This model can represent both an object’s boundary surface and its interior volume. The HSDM enables data reduction, while preserving sharp geometrical features and object topology. As a result the execution time of the reconstruction process is significantly reduced. Moreover, the proposed model naturally allows multiresolution surface reconstruction, represented by a mesh with regular properties. Based on the proposed volumetric model, the surface reconstruction process becomes more robust and stable with respect to sampling noise.

关键词： engineering graphics Noise (Sound) Topology Reverse engineering cad/CAM computer-aided design Octrees reverse engineering Algorithms octrees

来源：评论

学校读者我要写书评

暂无评论

Adaptive parameterization for reconstruction of 3D freeform objects from laser-scanned data

Adaptive parameterization for reconstruction of 3D freeform ...

引用

Pacific Conference on computer graphics and Applications

作者： A. Fischer A. Manor Y. Barhak CMSR Laboratory for Computer Graphical and CAD Department of Mechanical Engineering Technion Israel Institute of Technology-Technion Haifa Israel

关键词： Surface fitting Surface reconstruction Image reconstruction Reverse engineering Charge coupled devices Charge-coupled image sensors Least squares approximation Approximation methods

来源：评论

学校读者我要写书评

暂无评论

Verification of scanned engineering parts with cad models based on discrete curvature estimation

Verification of scanned engineering parts with CAD models ba...

引用

International Conference on Shape Modeling and Applications

作者： B. Lipshitz A. Fischer Laboratory for Computer Graphics and CAD Department of Mechanical Engineering Technion-Israel Institute of Technology Haifa Israel

The manufacturing industry constantly needs to verify machined objects against their original cad models. Given a prototype design, an engineer should be able to determine whether the part was manufactured well, that is, whether it fits the cad model exactly. However, derivative computations are unstable for real data, and the estimated curvature is thus very sensitive to noise. Moreover, in many cases, spatial fitting of corresponding points is not sufficient. The current work utilizes the curvature properties to inspect a manufactured part.

关键词： Smoothing methods Nonlinear filters Design automation Manufacturing industries Noise shaping Quality control Surface reconstruction Symmetric matrices Shape Laboratories

来源：评论

学校读者我要写书评

暂无评论

mechanically based design: adaptive refinement for B-spline finite element

Mechanically based design: adaptive refinement for B-spline ...

引用

International Conference on Shape Modeling and Applications

作者： P. Kagan A. Fischer P. Bar-Yoseph Laboratory for Computer Graphics and CAD Mechanical Engineering Department Technion-Israel Institute of Technology Haifa Israel Computational Mechanics Laboratory Mechanical Engineering Department Technion-Israel Institute of Technology Haifa Israel

ISBN: (纸本)0769508537

This paper presents a method for adaptive refinement within an integrated mechanically based CAE system. The system uses a mechanical B-spline finite element model for both geometric design and mechanical analysis. A technique for locally refining a solution by B-spline finite elements is presented. The key component in the proposed method is the linear coordinate transformation introduced into the refined element. The transformation is constructed in such a way that the transformed nodal configuration of the refined element is identical to the nodal configuration of the neighbor elements. Therefore, the assembly proceeds in the regular fashion, while the C/sup 0/ continuity is forced along the inter-element boundary exactly. The proposed adaptive refinement method has been implemented both for surface and solid design without substantial differences in technical complexity. Its feasibility as applied to sculptured surface and solid objects is demonstrated by several examples.

关键词： Spline Finite element methods computer aided engineering Shape Laboratories Solid modeling Algorithm design and analysis computer graphics Design automation mechanical engineering

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：