Research On Real-time CSCD Tools Based On Lightweight CAD Model

With the continuous development of CAD technology and the constant improvement of personalized customer demand, the traditional design mode of single-person stand-alone can not meet the requirements of the rapid exploitation of the enterprise design teams. Computer Supported Cooperative Design is the trend of CAD development, it enables develop-individuals or developers and customers participate in designing simultaneously in different geographic locations, improving the quality of design and develop efficiency. The real-time interactive cooperative is more meaningful that it can realize the simultaneous design without delay. The problem of Real-time cooperative design mainly focus on is remote screen sharing and remote cooperative synchronous operation, data exchange and real-time all-round exchanges and communication. Most of the real-time cooperative systems use electronic meeting tools, such as white board, video, remote control, but the real-time cooperative system aimed at product design objects(such as 2D drawings, 3D product models) is more meaningful for the sharing of product information. On the basis of predecessors' investigation, this paper will research and develop the real-time cooperative tools based on lightweight 3D models.The main research work are as follows:1. Discuss the technical solutions and system structure of real-time cooperative system to build a cooperative design system framework, which is stable, reliable and easy to develop and deploy, using C/S model to deploy the real-time cooperative tools and combining the PDM(Product Data Management) system to deal with the meeting information management based on B/S model.2. Use the lightweight CAD models (STL and OBJ) as design objects in real-time cooperation and analyze the advantages and disadvantages of this model in cooperative applications. In view of the limitation that this lightweight model does not contain the assembling information of a product, study how to extract the assembling information from the existing CAD model, transform them into lightweight models and re-display completely assembly model in the cooperative tool. Make a secondary development in VC++6.0 environment by using Pro/Toolkit of Pro/E.3. Discuss the key technologies of real-time cooperation, propose an information communication protocol by XML-based language, and an effective management model for the role of users in the real-time cooperative meeting. Peer-to-Peer communications are employed during cooperative process. Peer-to-Peer communications of WAN is related to the difficult problem of penetrating the firewall and NAT. This paper discusses the principles of how UDP penetrates NAT and experiments are carried out to verify the principle.4. Have developed a prototype tool CoViewer with functions of browsing and operation of the 3D lightweight models and mark-up by 2D, at the same time it has coordination functions such as chat with text and cooperation of the models.