A non-manifold feature-based approach for integrating mechanical conceptual design and assemblies.

摘要

Traditional design process is a serial process which is composed of inter-related sub-processes being cross-referenced by means of documentation such as engineering drawings and product specification. As the design information is fragmented, the consistency of design data is difficult to maintain. Some researchers had proposed the form feature modeling, which is a promising concept for capturing and maintaining design intentions. However, it is recognized that conventional 3D geometric modeling technology based feature models, including Constructive Solid Geometry (CSG) based, boundary representation (Brep) with manifold constraints and hybrid Brep/CSG representation, are not sufficient to support complete design life cycle activities. One of the reasons is that the vague shape being presented in the conceptual design phase cannot be captured and maintained by the conventional solid-based representation. As a result, the design intentions of the function structures being established in the early-design stage cannot be propagated to other design sub-processes.; Feature-based system can facilitate the design of mechanical assemblies by capturing the assembly topology and product geometry. The designer needs to evaluate the assemblability of the product, and the evaluation is better to be performed as early as possible in the design process. However, it is difficult, if not impossible, to apply the so-far developed solid-based FB methodology in the early-design environment. In order to rectify the problem, a non-manifold modeling domain is naturally required. However, the integration of non-manifold modeling with FB technology has only been reported on the domain of thin-walled components. Extensive research is required before an unified and rigorous design and assembly feature modeling methodology can be realized.; This thesis proposes the use of cell-complex based non-manifold FB design framework to develop a rigorous, concise and complete infrastructure for product modeling. The innovative works of this research involves the development of the scheme of cell-complex based non-manifold design and assembly feature modeling, the topological data structure for implementing the proposed feature modeling environment, and a mechanism for interrogating the feature database to achieve assemblability evaluation. The research also contributes to the state of the art by automating the assemblability evaluation for mechanical assembly by a geometric reasoning approach.