Geometric representation for Internet-based collaborative assembly design

The product assembly design activity requires extensive collaboration between designers who typically share assembly models and related design data. Due to the limited bandwidth of the Internet that is the medium of collaboration, the transfer of assembly models that are typically CAD models ranging in size from several megabytes to gigabytes is slow. Hence, polygonized representations of assembly models have been utilized for collaborative viewing while CAD models are utilized when detailed geometric modification of the models is required. This thesis presents a new geometric representation called the AREP that simplifies the assembly model in three stages and provides mechanisms not only for viewing assembly models but also supports geometric modifications of the existing models, integration of existing models into the current design and concurrent design of the product model. The first stage involves hierarchical simplification where components and subassemblies that are not required for a design session are eliminated. The second stage involves the simplification at the feature level, where either the geometric features that are required during assembly modeling are added to an envelope based representation of constituent components and subassemblies or geometric features that not required for assembly modeling are eliminated. The third stage involves simplification of geometry entities comprising the model. The proposed representation encapsulates geometric features required for assembly modeling and therefore helps designers to resolve specification conflicts early in the design phase. A prototypical system that uses the proposed representation to implement the collaboration paradigm is also presented. This system employs a three-tier client server based architecture that utilizes an intermediate intelligent server to redirect requests from clients to the appropriate server. This makes the system flexible, extensible and allows for decoupling of the CAD interface from the CAD modeling kernel, thereby providing a platform independent client interface to the CAD modeling kernel. The compactness of the representation for some typical assemblies is measured utilizing metrics proposed in this research and typical scenarios where the system allows the designers to effectively collaborate have been demonstrated.