From CAD assemblies toward knowledge-based assemblies using an intrinsic knowledge-based assembly model

ABSTRACT

CAD assemblies are essentially reduced to a set of components, often solids, and a user-defined tree structure. Given the generation process of CAD assembly models where the user may instantiate several times a given component, some solids may occur more than once. If this tree structure incorporates some functional information, this is not mandatory and it cannot be regarded as a reliable functional description. Similarly, component occurrences may not always end up being simple copies of a given solid. To this end, we introduce the concept of intrinsic assembly model and describe and illustrate an associated set of geometry processing operators that can produce an intrinsic shape descriptor of assembly components and extract assembly structure using symmetries, alignments, … As a complement, it is described how this intrinsic model can become an intrinsic knowledge-based assembly model. Some geometric concepts are mapped to symbolic information using ontology and new structural assembly information is derived using inferences. All these automated processes and mappings enforce the consistency of the proposed model. Illustrative examples show that this model is a first basis toward a functional description of an assembly where new inference rules can be added to express and characterize functional information. A website http://3dassblyanlysis.gforge.inria.fr/3d/ gives a public access to a knowledge-based assembly example (available with IE and Firefox navigators).

GRAPHICAL ABSTRACT

KEYWORDS:

• Assembly
• ontologies
• CAD models
• symmetry analysis
• repetitions
• shape similarity
• knowledge modeling
• B-Rep models
• RDF
• inference

Acknowledgments

The authors would like to thank the EEC through the ERC-EXPRESSIVE grant that partially contributed to support this research. Also, the authors thank EDF Lab that partially contributed to support this research.

ORCID

Harold Vilmart http://orcid.org/0000-0002-7849-8211

Jean-Claude Léon http://orcid.org/0000-0003-3337-081X

Federico Ulliana http://orcid.org/0000-0002-9192-9573