【摘要】 在 Internet网上由于网络带宽限制等多方面的原因 ,远程产品协同设计实时交互是无法达到的 .为此 ,基于现有的软硬件环境及实际需要 ,该文提出了一个以集中模式与分布模式混合构造的“类实时交互”模型 ,使 CAD系统的交互层次上升到操作语义信息 .同时文中首次提出了 CAD操作命令交换标准 STEC,并以 CORBA中 IDL语言定义了工程 CAD系统与 STEC之间的映射 .实践表明 ,该模型便于跨平台工作 ,加快了远程产品设计中有效信息的相互交流与实时协同更多还原

【Abstract】 The real time interaction has been a hot spot in Network CAD. It mainly focuses on how to use computer technology to support synchronous interaction in CAD among distributed cooperative members. According to the limitation of network bandwidth and other reasons over Internet, it is impossible to achieve the real time intercommunication in distant product design. With the current conditions of software and hardware and demand for practice, a model of "Nominal Real Time Interaction(NRTI)" constructed with concentration and distribution patterns is presented. The model works as follows: ①initialize the distributed CAD systems; ②operate in a CAD system; ③obtain the commands and results of the new operation; ④translate the new CAD information into the neutral CAD information; ⑤transfer the information to the other CAD system through Internet; ⑥translate the neutral CAD information into the commands and results of the new CAD operation; ⑦operate in the new CAD system; ⑧go to ② in order to continue. The basic idea of NRTI is to encapsulate additional operation information of CAD system to achieve real time interaction of the design objects and process by the event driven synchronization and timing sequence synchronization, which makes the interaction level in CAD systems up to that of semanteme for operation information. Moreover, NRTI includes two levels: AutoCAD based NRTI and information interaction standard based NRTI, and two patterns: the concentrative NRTI and the distributed NRTI. The concentration pattern of NRTI is often used to initialize the CAD system environment, while the distribution pattern is used to transmit and operate the CAD data. In addition, the STandard for the Exchange of Command in computer aided design(STEC) is also presented for the first time, including its object, conforming principles, meta sentence, command and functional extension language SLISP. Lastly we define the mutual mapping of engineering CAD and STEC by IDL of CORBA, which provides the feature of standard and practibility in STEC. By analysing the experiments, the model of NRTI can easily work in different platforms, and improves intercommunication and real time cooperation of effective information in distant product design.更多还原