一种改进型的S^4PR网活性条件

An Improved Liveness Condition for S^4PR Nets

研究了顺序资源共享分配系统的建模模型S4PR(Systems of sequential systems with shared resources)网的活性问题.已有的研究成果表明,一个S4PR网在所有信标都满足max,max或max-controlled时能保持活性,但现有的活性条件对信标的限制严格且不适用于某些网系统,本文提出了一类名为max*-controlled的改进型条件,并证明了当一个S4PR网的所有信标都满足max*-controlled条件时,网系统能保持活性.与现有的其他条件相比,新的活性条件更加宽松,为设计更高允许度的死锁预防或者活性保持监控器提供了理论支撑.

This paper studies the liveness problem for S4PR （systems of sequential systems with shared resources） nets, a class of Petri net models of flexible manufacturing systems. Current research indicates that an S4PR net is live if all its siphons are max, max′, or max″-controlled. However, these conditions tend to be overly restrictive and are not available to some net systems. This paper presents an improved condition called max＊-controlled condition and proves that an S4PR net is live if all its siphons are max＊-controlled. Compared with the preceding ones, this new condition is more general and can be a theoretical support for designing deadlock prevention or liveness-enforcing supervisor which is more permissive on system behavior.