Martti Mäntylä

Feature modelling by incremental feature recognition

Abstract A novel feature-modelling system which implements a hybrid of feature-based design and feature recognition in a single framework is described. During the design process of a part, the user can modify interactively either the solid model or the feature model of the part while the system keeps the other model 3onsistent with the changed one. This gives the user the freedom of choosing the most convenient means of expressing each required operation. The system is based on a novel feature recognizer that provides incremental feature recognition , which allows changes to a geometric model to be recognized as new or modified features while preserving previously recognized features that remain unchanged in the geometric model. Each recognizable feature type is specified by means of a feature-definition language which facilitates the addition of new feature types into the system.

Functional Understanding of Assembly Modelling

Abstract Conceptual design requires the evolution of modelling methodology beyond geometric and feature modelling. The functional understanding of assemblies is a key means to this end. A general top-down assembly model is presented that can provide both a function-oriented view and a module-oriented view of the assembly structure. The former is related to functional and behavioural knowledge, and the latter to manufacturing knowledge. A mixed dimensional geometric-modelling environment is interfaced with the top-down assembly design process. Therefore, assembly models at various levels of detail can be generated and converted to each other. An experimental modelling system, †, illustrates how the modelling scheme can be realized.

Challenges in feature-based manufacturing research

ion Figure 8. A piece of stock, a bracket to be machined from the stock, and the delta volume Countersink-hole Process: Twistdrlling Reamed-hole Counter-sink Free-hole Process: Twistdrlling

Knowledge Intensive CAD

The ultimate goal of advanced computer-aided design technologies is to facilitate effective product design and manufacturing activities in industrial companies through the whole lifecycle of industrial products. A central means for achieving this long-term goal is turning various types of knowledge on industrial products, their manufacture, use, maintenance, and other life-cycle activities into a reusable resource for the company, and deploying the resulting life-cycle knowledge during product development and manufacture, particularly the early design stages. It is claimed that these two-knowledge capitalisation and knowledge deployment-are essential characteristics of a Knowledge-Intensive CAD environment. Based on this view, the paper will discuss some of the characteristics, issues, and challenges of knowledge-intensive CAD systems, and give a draft research agenda for future.

Localized set operations for solid modeling

Set operation algorithms form an important component of solid modeling systems. Their efficiency can be enhanced by localizing the search for geometric intersections to the region of overlap using a spatial directory. We present an algorithm that employs a three-dimensional extendible cell (EXCELL) directory to the set operation problem, and demonstrate by practical experiments the efficiency and the local nature of the algorithm.

Integration of Functional and Feature-Based Product Modelling - The IMS/GNOSIS Experience

Abstract This article describes collaborative research carried out in the project GNOSIS, one of the six test cases of the proposed international research programme IMS. A joint demonstration combining tools and methods from several partners was created to experiment supporting the flow of models and processes involved in the various stages of product realization including design, manufacturing preparation, and manufacturing. The article discusses the product modelling part of the joint demonstration. The process covered begins from a creative design state where a functional product description is created using the SYSFUND system of the University of Tokyo. The functional structure is passed on to the MCOES, system of the Helsinki University of Technology; in MCOES, the functional model is mapped to a physical structure for creating an assembly family. The most interesting result of the demonstration is the experience on the information flow and the gaps between these two systems.

A note on the modeling space of Euler operators

Abstract Alternative modeling spaces for physical solid objects are discussed and it is shown that the so-called Euler operators completely describe the family of objects bounded by 2-manifold surfaces.

Ray-casting and block model conversion using a spatial index

Abstract A spatial index is a data structure designed to facilitate spatial search, exemplified by the point-in-polyhedron inclusion problem. The 3D extensible cell (EXCELL) index is presented together with algorithms for spatial search and for converting a complex polyhedron (boundary representation) into an octree-like block model. We illustrate the techniques by an application to geometric mine modelling and demonstrate the efficiency of the approach by practical experiments.

Space sweep solves intersection of convex polyhedra

SummaryPlane-sweep algorithms form a fairly general approach to two-dimensional problems of computational geometry. No corresponding general space-sweep algorithms for geometric problems in 3- space are known. We derive concepts for such space-sweep algorithms that yield an efficient solution to the problem of solving any set operation (union, intersection, ...) of two convex polyhedra. Our solution matches the best known time bound of O(n log n), where n is the combined number of vertices of the two polyhedra.

An inversion algorithm for geometric models

Instead of storing boundary models of solids directly into a data base, it would be advantageous to map them first into a simpler form. This approach calls for a procedure called in this paper the inversion algorithm of a geometric model. We present and analyze an inversion algorithm which constructs a sequence of Euler Operators capable of creating a given boundary representation. The algorithm is completely based on the use of Euler Operators enabling us to keep the algorithm simple and to hide implementation and data structure details.