Caracterisation semantique des differences entre des modeles CAO par transposition des contraintes geometriques explicites

Represented within numerous models, a product's geometric definition evolves continuously through the work of many specialists as they use, analyze and modify product data, making decisions and engaging in actions accordingly. Many times during a product's lifecycle, a geometric evolution will develop from one of these models, acknowledged as expert models, which will then have to be propagated to the other expert models to maintain coherence throughout the product's definition. The modifications to each model, however, will need to be specific. Thus, effective transposition of shape changes between two distinct expert models depends on the adapted representation and ensuing interpretation of the geometric delta relating to the view of the product embodied by the expert model to which the shape change is propagated. Assuming the product's geometric definition as the common constituent of a federation of expert models, and acknowledging the dispersal - as opposed to the integration - of these models throughout the extended enterprise, this doctoral thesis examines geometric comparison as a solution to the shape change transposition problem. The goal is to develop a new comparison approach for assessing the geometric differences between two expert models of a mechanical component through adequate semantics, thereby enabling the interpretation and assimilation of a geometric delta from the specific viewpoint of an engineering domain. Attention is specifically given to the precision in geometric difference calculation, the intuitiveness of the difference representation for mechanical engineers and the functionality of such representations from a product lifecycle management (PLM) perspective. The state of the art on 3D CAD model comparison, from the three perspectives of the application scenarios, the difference calculation methods and available software tools, has led to the assertion that model comparison applications are numerous and that shape change transposition relates to those applications requiring model difference identification (MDI) solutions. This assertion was confirmed here through software tool evaluation trials which revealed that no MDI technology can be applied conveniently whatever the model comparison scenario. Those trials also exposed issues in difference representation for existing software solutions. Consequently, a framework for structuring and characterizing 3D CAD model comparison scenarios is proposed. The 3D CAD model comparison approach presented in this thesis processes explicit geometric constraints, detailing the original shape with respect to an abstraction level familiar to engineers and from the specific viewpoint of their domain, to assess the geometric delta differentiating the new shape from the original. This approach combines the mapping of topological elements from the original and modified boundary representations (B-Rep), the transposition of geometric constraints from the original to the modified shape one and the representation of those mappings and derived differences via a new difference model inspired from model-driven software engineering (MDSE). Hence, it enables the expression of the geometric delta characterizing the product definition evolution in terms of original dimensional constraint deviations and/or some geometric constraints' deletion or violation.