【摘要】 基于Petri网,研究了一类柔性制造系统中由可被清空的信标引发死锁的一种预防策略.将Petri网中可被清空的信标分为基本信标和从属信标,给每个基本信标添加一个控制库所.通过调节信标的控制深度变量,可控制所有的从属信标,并提出从属信标受控时所应满足的条件.通过对控制器的结构分析和优化设计,提出一种判断控制库所是否冗余的方法.通过剔除冗余的控制库所,得到了结构更为简单,许可行为更多的活性Petri网控制器.更多还原

【Abstract】 This paper develops a deadlock prevention policy for a class of Petri nets,which can model a wide class of flexible manufacturing systems,where deadlocks are caused by unmarked siphons.We distinguish emptiable siphons in a plant Petri net model by elementary and dependent ones. By adding a control place(monitor) for each elementary siphon,all dependent siphons can be controlled by adjusting control depth variables of elementary siphons.A prior condition is developed under which a dependent siphon can be implicitly controlled.Furthermore,by structural analysis and optimization design of a supervisor,a method is proposed to decide whether an additional control place is redundant.By removing control-redundant control places,a simplified liveness-enforcing supervisor with more permissive behavior can be obtained.更多还原