A semantic model difference identification (MDI) solution can be defined as an MDI solution that identifies and represents the differences between two compared models in terms of meaningful engineering information. Semantic representation of the differences between 3D CAD models is especially challenging due to the variety of modeling solutions used across industries, the non-uniqueness of modeling sequences and the use of low-level information, e.g. B-rep STEP files, in engineering communications. This work proposes an MDI method that represents the differences between 3D CAD models based on engineering semantics through features. Brake-and hydro-formed aerospace sheet metal parts are used as the application domain in which to propose and illustrate the proposed method. This method consists mainly of a pose registration stage and a difference identification stage. The pose registration method considers that all the features of a part serve specific functions, some of which are fundamental to the part's essential functionality, and that they are intertwined with the design intent of the part, which is particularly true for aerospace sheet metal parts. This provides the opportunity to semantically register feature-based 3D CAD models according to the unique purpose of the features in this specific domain of application. Difference identification is approached by primarily identifying and segregating the commonality between the compared 3D CAD models and then identifying the differences. The differences between 3D CAD models are classified as added, removed or differed features. Differed features are those features that are of the same type, but whose definition varies. As an outcome, the proposed method describes a way to fully pose-register 3D CAD models and identify their differences semantically based solely on their features, and, by extension, their design intent.

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