混合语义时间Petri网模型

Time Petri Net Model with Mixed Semantics

提出了时间Petri网的混合语义模型,通过在变迁及其非冲突变迁集的最小上界处设置强制实施点,排除冲突变迁对变迁可实施性的影响,达到既能扩大模型调度范围又可保证任务调度时限性的目的,以解决现有语义模型在调度分析上的缺陷.进一步证明了混合语义模型的图灵等价性及标识可达性问题的不可判定性,然后界定了3种语义模型的时间语言接受能力.最后提出了状态类分析方法,用于模型的可调度性分析和时间计算,并以一个柔性制造系统为例,比较和验证了3种语义模型的调度分析能力.

This paper presents a time Petri net （TPN） model with mixed semantics that efficiently addresses the schedulability analysis problem of the existing semantics models.The proposed model associates each firable transition with a mandatory firing point that is set to the least upper bound of the transition and its non-conflicting transitions.This treatment not only eliminates the effect of conflicting transitions on the transition friability and extends the scheduling scope of the TPN model,but also ensures the time limit of the task scheduling.To determine the expressiveness of the mixed model,the study proves that the mixed semantics model has the power of Turing machines and its marking reachability problem is undecidable.The timed expressiveness of three semantics models with respect to timed language acceptance is also compared.A state class approach is then proposed for the scheduling analysis of the mixed model.Finally,a flexible manufacturing system is used as an example to compare the scheduling ability of three semantics models.