英语论文网

3D [11] that supports collaborative assembly/disassembly over Internet and presented systematic methodology for disassembly relation modeling, path/sequence automatic generation and evaluation independent of any commercial CAD systems. Shyamsundar et al. developed an internetbased collaborative product assembly design (cPAD) tool [12][13]. The architecture of cPAD adopts 3-tier client/server mode. In this system, a new Assembly Proceedings of the Second International Conference on Embedded Software and Systems (ICESS’05) 0-7695-2512-1/05 $20.00 © 2005 IEEE Authorized licensed use limited to: MACQUARIE UNIV. Downloaded on July 5, 2009 at 22:47 from IEEE Xplore. Restrictions apply. Representation (AREP) scheme was introduced to improve the assembly modeling efficiency. The AREP model at the server side can be accessed by many designers at different locations through client browsers implemented using Java3D. But most CVA systems above are based on C/S or B/S architecture, and little effort has been put into the research of CVA based on distributed architecture. Sometimes there are some requirements on the design of certain industrial products, which expect a distributed virtual environment to support the collaborative assembly, such as a Virtual Environment for Collaborative Assembly (VECA) presented in this paper. VECA can build a collaborative virtual assembly system which allows geographical dispersed engineers to perform an assembly task together. VECA mainly includes HLA-based (High Level Architecture) communication and collaboration, motion guidance based on collision detection and assembly constraints recognition, data translation from CAD to virtual environment, reference resolution in multimodal interaction, and so on. The rest of this paper is organized as follows. Section 2 presents the system architecture of VECA. The modules of communication and collaboration, data translation, motion guidance, multimodal interaction are separately elaborated in section 3, 4, 5, and 6. Section 7 is the implementation and application of VECA, and finally section 8 ends this paper with conclusions and future work. 2. System Architecture The system architecture of VECA is illustrated in Fig.1. Once an engineer has finished designing assemblies or subassemblies using a parametric CAD system such as Pro/Engineer, he or she uses a plug-in for Pro/Engineer to translate CAD models to triangle mesh models (Multigen OpenFlight) including assembly constraints and geometry feature information. Others download these models, and then they can assemble the product collaboratively in a multimodal shared VE to find the design defects or get the feasible assembly sequence. Now there are five key parts in the system. 1. Communication and collaboration: connects geographical dispersed nodes to form a distributed collaborative VE based on HLA. 2. Motion guidance: helps the user translate or rotate the parts in the VE freely and precisely using collision detection and assembly constraints recognition. 3. Data translation: this module translates models and extracts information from CAD (Pro/Engineer). It is a plug-in for Pro/Engineer and is developed by Pro/Toolkit and Multigen OpenFlight API. 4. Constraint manager: dynamically maintains assembly constraints information. The design of this module and a constraint-based distributed virtual assembly model were already introduced in [14][15]. 5. Multimodal interaction: processes combined natural input modes such as spe