基于扩展Petri网的混合流程生产过程建模

提出了一种扩展的 Petri网建模语言 (Hy Net) ,该语言将面向对象技术、谓词逻辑和微分方程融入高级Petri网中 ,把托肯 (token)作为对象 ,利用弧变量将库所 (place)中托肯携带的信息传递到其后置变迁。这些信息可用来控制变迁的使能条件、规定变迁的活动和计算变迁的激发延续时间。因此 ,这种语言具有很强的模型描述能力 ,利用它所建的模型具有很好的柔性。作为案例 ,文中利用该语言建立了一个具体的混合流程企业的生产过程模型。

An Extended Petri Net for Modeling Batch Processes

A new kind of extended Petri net, which is called HyNet, is presented in this paper. The net is defined as a set of three elements (P, T, A), where P is the place set, T is the transition set and A is the arc set that connects between P and T. The HyNet has several outstanding characteristics compared with the usual Petri net. First, tokens in the HyNet are defined as instance of classes. Information about production process is integrated into token, so the structure of the HyNet will not change when the production process changes. Second, selecting rules are added into places, so the flexibility of the HyNet is increased. Third, arc variables are introduced in the HyNet. They can transmit information from token to transition. Finally, in order to avoid confusion and conflict, inciting abilities, enabling conditions, inciting actions and inciting time are introduced into the HyNet as constraints for the transitions. Based on the HyNet, a process model of a batch processes is set up. Some difficult problems related to the process model, such as the conflict among resources and the concurrence among transitions, are studied in detail, and the solutions for the problems are also given.