CAD: from geometrical to functional modelling

CAD is still largely based on geometric modeling, particularly morphological aspects (geometric modeling [H 3 750] ). It is therefore, by its very nature, quite remote from functional design, although it does constitute a fundamental building block. The challenge now is not simply to be able to model the morphology of an object, but to implement a systemic approach that starts with the specifications and ends with a product, taking into account the intermediate phases, whether virtual (simulations...) or real (manufacturing...) and subsequent (use, recycling...).

In particular, this article aims to demonstrate that one of the solutions is to consider CAD as the most upstream tool, and by enriching it and linking it to other technologies, to move towards a more functional design. We will see how recent developments, or improvements in the near future, can make it easier for CAD systems to take functions into account, starting with geometric modeling. Developments have made it possible to circumvent a number of the limitations of geometric models, without however leading to totally innovative solutions. It is therefore important to understand these developments and their integration in a context where CAD must take account of other technologies such as knowledge management and simulation.

The first attempt to enrich geometric models was to add technological information, such as a layer based on geometry. We therefore present feature-based design, detailing some of the algorithms that enable us to understand how "modern" CAD systems work.

Staying with the same approach of enriching geometric modeling, this article then presents methodologies and models for integrating CAD with knowledge management, and then with digital simulation/optimization. It is indeed necessary to master not only the technical aspects, but also the methodologies that are useful for solving problems that are multi-model in nature.

The multi-modeling inherent in the fact that there is no such thing as a single CAD model is even more striking when we consider the different technologies (simulation, etc.). Before concluding, this article offers an overview of the issues involved in exchanging and sharing data.