Identification de caractéristiques de forme et de structure d’assemblages de pièces CAO pour la recherche dans des bases de données

The large use of CAD systems in many industrial fields, such as automotive, naval, and aerospace, has generated a number of 3D databases making available a lot of 3D digital models. Within enterprises, which make use of these technologies, it is common practice to access to CAD models of previously developed products. In fact, designing new products often refers to existing models since similar products allow knowing in advance common problems and related solutions. Therefore, it is useful to have technological solutions that are able to evaluate the similarities of different products in such a way that the user can retrieve existing models and thus have access to the associated useful information for the new design.The concept of similarity has been widely studied in literature and it is well known that two objects can be similar under different perspectives. These multiple possibilities make complicate the assessment of the similarity between two objects. So far, many methods are proposed for the recognition of different parts similarities, but few researches address this problem for assembly models. If evaluating the similarity between two parts may be done under different perspectives, considering assemblies, the viewpoints increase considerably since there are more elements playing a meaningful role.Based on these requirements, we propose a system for retrieving similar assemblies according to different similarity criteria. To achieve this goal, it is necessary having an assembly description including all the information required for the characterizations of the possible different similarity criteria between the two assemblies. Therefore, one of the main topics of this work is the definition of a descriptor capable of encoding the data needed for the evaluation of similarity adaptable to different objectives. In addition, some of the information included in the descriptor may be available in CAD models, while other has to be extracted appropriately. Therefore, algorithms are proposed for extracting the necessary information to fill out the descriptor elements. Finally, for the evaluation of assembly similarity, several measures are defined, each of them evaluating a specific aspect of their similarity.