关键词: Petri网, 虚拟装配环境, 装配模型, 装配过程仿真

Abstract: Through analyzing the structure and characteristics of Virtual Assembly Environment (VAE), a Knowledgebased Hierarchical ObjectOriented Timed Petri Net (KHOOTPN) was defined, and the application layer model of VAE based on KHOOTPN was constructed to address the limitations of the scene graph structure in virtual assembly application. With the input of posture and position of virtual hand, the model outputted the event for updated scene graph to realize the activity of virtual assembly. Thus the requirements of realtime and concurrence of VAE were satisfied, and the treatment of large number of discrete events and capture of assembly intention were also realized. Furthermore, the representation of assembly model based on KHOOTPN was proposed, which could not only represent the structure and assembly relationship of a product, but also record dynamic information such as the position and constraint state of each component in the process of assembly. Therefore, both the assembly and disassembly were implemented in VAE. Moreover, the algorithm of generation of KHOOTPNbased assembly model from assembly hierarchical graph was presented. Based on application layer model, the operation of assembly and disassembly, as well as the simulation of assembly process, were also illustrated. Finally, the prototype system was developed.

Key words: Petri net, virtual assembly environment, assembly model, assembly process simulation