Commercial Computer-aided Design Packages Research Articles

A bi-directional interface for improved interaction with engineering models in virtual reality design reviews

Leveraging virtual reality (VR) technology to enhance engineering design reviews has been an area of significant interest for researchers since the advent of modern VR. The ability to interact meaningfully with 3D computer-aided engineering models in these VR design reviews is an important, though often neglected, capability due to the difficulty of performing data translation between native computer-aided design (CAD) data and VR compatible file formats. A bi-directional interface was developed between a VR design review environment and a commercial CAD package that streamlines the data translation process. Transmitting both geometric data and selected metadata from the CAD system enabled the development of enhanced model interaction tools in a VR design review application. User experiments were performed that compared the enhanced tools developed to a baseline toolset. Participants success using these toolsets was measured as they performed tasks related to design understanding and decision making, such as counting the number of gears in a gearbox or evaluating the feasibility of a proposed design change in a four-cylinder engine. The analysis of the data from these experiments showed a statistically significant improvement in participants ability to understand the geometry of the model correctly, confidently, and quickly, as well as in participants ability to correctly and confidently understand the implications of a proposed design change when using the Enhanced Toolset. We conclude that the bi-directional interface concept developed in this work can be extended to enable advanced interaction with a diversity of engineering data in VR.

Integrating CAD with Abaqus: A practical isogeometric analysis software platform for industrial applications

Isogeometric analysis (IGA) has been developed for more than a decade. However, the usage of IGA is by far limited mostly within academic community. The lack of automatic or semi-automatic software platform of IGA is one of the main bottlenecks that prevent IGA from wide applications in industry. In this paper, we present a comprehensive IGA software platform that allows IGA to be incorporated into existing commercial software such as Abaqus, heading one step further to bridge the gap between design and analysis. The proposed IGA software framework takes advantage of user-defined elements in Abaqus, linking with general. IGES files from commercial computer aided design packages, Rhino specific files and mesh data. The platform includes all the necessary modules of the design-through-analysis pipeline: pre-processing, surface and volumetric T-spline construction, analysis and post-processing. Several practical application problems are studied to demonstrate the capability of the proposed software platform.

Automated Generation of Repeated Geometric Patterns for Customized Additively Manufactured Personal Products

Aesthetic patterning of free-form surfaces is difficult and time consuming, especially for a non-expert user of a 3D Computer-aided design (CAD) system. This paper presents a computational method for automatically generating aesthetic patterns based on minimal user input. The system produces anisotropic geometric feature patterns in three-steps: (1) model preparation, (2) feature interpolation via a tensor field and bubble packing, and (3) pattern generation on a selected surface using standard Boolean operations and CAD engine primitives (e.g., points, planes, and ellipses). The user inputs a small number of geometric features called “seed features” with the desired size and orientation in preferred locations within the target area. The tool generates the location, anisotropic size, and orientation of geometric features while preserving the target-area boundaries. These geometric seed features are then transformed into tensors and used as boundary conditions to generate a Riemannian metric tensor field that represents the anisotropic attributes of the features. A form of the Laplace's heat equation is used to produce the field over the target domain which is subject to the specified boundary conditions. The structure and the field described by Laplace's equation determines the geometric features and increases them whenever this field has the greater value. Repeated geometric patterns are then generated on a free-form curved surface by packing elliptical cells. This process was developed as an add-on for a commercial CAD package. All the features can be edited further within the CAD software if the user desires. In this paper we demonstrate the application of the proposed automated patterning method to additively manufactured personal products.

Automatic Generation of Anisotropic Patterns of Geometric Features for Industrial Design

While modern computer aided design (CAD) systems currently offer tools for generating simple patterns, such as uniformly spaced rectangular or radial patterns, these tools are limited in several ways: (1) They cannot be applied to free-form geometries used in industrial design, (2) patterning of these features happens within a single working plane and is not applicable to highly curved surfaces, and (3) created features lack anisotropy and spatial variations, such as changes in the size and orientation of geometric features within a given region. In this paper, we introduce a novel approach for creating anisotropic patterns of geometric features on free-form surfaces. Complex patterns are generated automatically, such that they conform to the boundary of any specified target region. Furthermore, user input of a small number of geometric features (called “seed features”) of desired size and orientation in preferred locations could be specified within the target domain. These geometric seed features are then transformed into tensors and used as boundary conditions to generate a Riemannian metric tensor field. A form of Laplace's heat equation is used to produce the field over the target domain, subject to specified boundary conditions. The field represents the anisotropic pattern of geometric features. This procedure is implemented as an add-on for a commercial CAD package to add geometric features to a target region of a three-dimensional model using two set operations: union and subtraction. This method facilitates the creation of a complex pattern of hundreds of geometric features in less than 5 min. All the features are accessible from the CAD system, and if required, they are manipulable individually by the user.

Interactive three-dimensional visualization and creation of geometries for Monte Carlo calculations

The implementation of three-dimensional geometries for the simulation of radiation transport problems is a very time-consuming task. Each particle transport code supplies its own scripting language and syntax for creating the geometries. All of them are based on the Constructive Solid Geometry scheme requiring textual description. This makes the creation a tedious and error-prone task, which is especially hard to master for novice users. The Monte Carlo code FLUKA comes with built-in support for creating two-dimensional cross-sections through the geometry and FLUKACAD, a custom-built converter to the commercial Computer Aided Design package AutoCAD, exists for 3D visualization. For other codes, like MCNPX, a couple of different tools are available, but they are often specifically tailored to the particle transport code and its approach used for implementing geometries. Complex constructive solid modeling usually requires very fast and expensive special purpose hardware, which is not widely available. In this paper SimpleGeo is presented, which is an implementation of a generic versatile interactive geometry modeler using off-the-shelf hardware. It is running on Windows, with a Linux version currently under preparation. This paper describes its functionality, which allows for rapid interactive visualization as well as generation of three-dimensional geometries, and also discusses critical issues regarding common CAD systems.

Analysis and design of cavity-coupled microstrip couplers and transitions

This paper describes a full-wave moment-method analysis of an aperture-coupled microstrip coupler using a resonant cavity (rectangular or circular) between the substrate ground planes. Structures of this type are useful for millimeter-wave integrated circuits and phased arrays, as they allow the use of a relatively thick central ground plane to provide isolation, as well as heat dissipation. Both four-port coupler geometries and two-port transitions are treated. Equivalent circuits are derived for each of these problems, and computed results are validated with data from the literature and with independent calculations from commercial computer-aided design (CAD) packages and measured data. These comparisons show that the solutions derived here are accurate and computationally efficient, and have the added advantage over commercial CAD packages in that equivalent-circuit parameters can be obtained directly. The vector Bessel transform is used to derive the required Green's function for the circular cavity.

Adaptive reconstruction of free-form surfaces using Bernstein basis function networks

Many computer graphics and computer-aided design (CAD) applications require mathematical models to be generated from measured coordinate data. The three-dimensional surface model of a complex object can be created by fitting the data with low-order parametric surface patches, and adjusting the control parameters such that the constituent patches meet seamlessly at their common boundaries. Most neural networks that are designed for function approximation produce a solution that is not easily transferable to CAD software. An adaptive technique to reconstruct a smooth surface from Bézier patches is presented in this paper. The approach utilizes a neural network that performs a weighted summation of Bernstein polynomial basis functions. The number of basis neurons is related to the degree of the Bernstein polynomials and is equivalent to the number of control parameters. Free-form surfaces are reconstructed by simultaneously updating networks that correspond to the separate patches. A smooth transition between adjacent Bézier surface patches is achieved by imposing positional and tangential continuity constraints on the weights during the adaptation process. The final weights of the various networks correspond to the control points of the stitched Bézier surface, and can therefore be used directly in many commercial CAD packages. This method has been used to create a closed surface by adaptively fitting two adjacent patches to synthetic range data and a complex open surface by fitting four patches to experimentally measured range data.

A CAD-based computer vision system

A vision system for recognizing rigid and articulated three-dimensional objects in two-dimensional images is described. Geometrical models are extracted from a commercial computer aided design package. The models are then augmented with appearance and functional information which improves the system's hypothesis generation, hypothesis verification, and pose refinement. Significant advantages over existing CAD-based vision systems, which utilize only information available in the CAD system, are realized. Examples show the system recognizing, locating, and tracking a variety of objects in a robot work-cell and in natural scenes.