The Automatic Adaptation For CAD Models

Case-Based Design is an effective approach for producing impressive and innovative designs easier and faster. However, the effect of Case-Based Design is still far from being satisfactory, which is mainly caused by the fact that the retrieved design cases are usually very difficult to adapt themselves to the new design requirements automatically. Currently, the works about design case adaptation are often human-dependent and time-consuming, which affects the efficiency of Case-Based Design approach seriously. The automatic adaptation for CAD models is studied in this dissertation. Focusing on how to make the CAD models, which mainly composed of feature-based parametric models and assembly models, automatically modify themselves according to the new requirements, this dissertation aims to improve the efficiency and quality for CAD model adaptation considerably, such that the effect of Case-Based Design in embodiment design and detail design can be effectively improved.The main contents of the dissertation are presented as follows:(1) Automatic adaptation for feature-based parametric modelsAn automatic adaptation approach for feature-based parametric models is presented according to the characteristics of feature-based parametric models. First, to determine the corresponding faces between two feature-based parametric models, a shape frame concept and its quantitative descriptor are defined. Second, to unify the representation of seemingly different but inherently consistent dimensions, a dimension promotion method is adopted. Third, based on the corresponding faces and the promoted dimensions, the corresponding dimensions and corresponding dimension chains between two feature-based parametric models are identified. Finally, based on dimension value transferring, the automatic adaptation for feature-based parametric models is achieved. The proposed approach can effectively achieve the automatic and high quality shape adaptation for feature-based parametric models.(2) Automatic adaptation of assembly modelsBased on the mechanism of each assembly model, a hierarchical automatic adaptation approach for assembly models is presented. First, in order to identify the corresponding links and interfaces between two assembly models, an attributed kinematic graph is put forward and adopted. Second, based on the attributed kinematic graph, automatic kinematic semantics adaptation can be achieved for an assembly model. Third, according to the geometry correspondences and the semantics adaptation result, through performing link layout transferring, automatic geometry adaptation for an assembly model can be achieved. The approach enables each assembly model to achieve automatic adaptation both on semantic level and geometric level.(3) Automatic adaptation for subparts of feature-based parametric modelsAn automatic adaptation approach for subparts of feature-based parametric models is present based on the characteristics of reusable subparts. First, to determine the corresponding faces between two subparts, a seed face filter method is adopted. Second, to explicitly represent the dimensions and location information of a subpart, a local 3D constraint graph is adopted. Finally, based on the corresponding face and the 3D constraint graph, a subpart’s shape and location information can be automatically modified through dimension transferring and constraint transferring respectively. The proposed approach can effectively achieve automatic adaptation for reusable subparts of feature-based parametric models.Based on the above researches, a prototype system MAdaptation is designed to validate the proposed approaches.