Deadlock avoidance of flexible manufacturing systems (FMSs) has received increasing attention from both academic and industrial communities. There have been a large number of different types of deadlock avoidance policies discussed in the literature. However, how to avoid deadlocks in an efficient way is still one of the major obstacles, especially for large systems. In this paper, we propose a new Petri net structure, i.e., event circuit structures ( $ESs$ ), based technique to overcome this difficulty. First, we provide details of $ESs$ and develop an algorithm to calculate $ESs$ in the systems of sequential systems with shared resources ( $S^{4}Rs$ ). Second, we analyze the liveness of $S^{4}Rs$ using undermarked $ESs$ . A necessary and sufficient condition between undermarked $ESs$ and deadlocks of $S^{4}Rs$ is established. Third, we describe how undermarked $ESs$ can be applied to avoid deadlocks for $S^{4}Rs$ . Only structure information is needed during this procedure, thereby improving the efficiency and convenience of deadlock avoidance. Several examples are presented to illustrate our approach. Note to Practitioners—Deadlock avoidance of flexible manufacturing systems (FMSs) is extremely important in real-world manufacturing scenarios. A large body of deadlock avoidance policies are presented in the existing literature. Through an effective deadlock avoidance policy, all deadlocks can be prevented from happening in advance, so as to avoid the reallocation of resources and the re-execution of deadlocked processes. This shortens the production cycle of systems and improves the utilization of resources. However, most existing approaches suffer from formidable computational difficulty since they necessarily rely on the whole reachability graph to avoid deadlocks. In this paper, we present event circuit structures ( $ESs$ ) as a new technique for deadlock avoidance. We show that undermarked $ESs$ can be used to avoid deadlocks by using only key structure information instead of complicated state information. Thus, it not only can greatly improve the efficiency of predicting deadlock markings for FMSs, but also reduce operating costs as much as possible while ensuring stable operation of FMSs.

中文翻译：

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柔性制造系统中避免死锁的事件电路结构


柔性制造系统（FMS）的死锁避免越来越受到学术界和工业界的关注。文献中讨论了大量不同类型的死锁避免策略。然而，如何有效地避免死锁仍然是主要障碍之一，特别是对于大型系统。在本文中，我们提出了一种新的Petri网结构，即事件电路结构（$ESs$），基于技术来克服这个困难。首先，我们提供 $ESs$ 的详细信息，并开发一种算法来计算具有共享资源的顺序系统（ $S^{4}Rs$ ）中的 $ESs$ 。其次，我们使用带下划线的 $ESs$ 分析 $S^{4}Rs$ 的活跃度。下标 $ESs$ 与 $S^{4}Rs$ 死锁之间的充要条件成立。第三，我们描述如何应用带下划线的 $ESs$ 来避免 $S^{4}Rs$ 的死锁。该过程中只需要结构信息，提高了避免死锁的效率和便利性。给出了几个例子来说明我们的方法。从业者注意事项——避免柔性制造系统 (FMS) 的死锁在现实制造场景中极其重要。现有文献中提出了大量避免死锁的策略。通过有效的死锁避免策略，可以提前阻止所有死锁的发生，从而避免资源的重新分配和死锁进程的重新执行。这缩短了系统的生产周期，提高了资源的利用率。然而，大多数现有方法都面临着巨大的计算困难，因为它们必须依赖整个可达性图来避免死锁。 在本文中，我们提出事件电路结构（$ESs$）作为避免死锁的新技术。我们证明，通过仅使用关键结构信息而不是复杂的状态信息，可以使用带下划线的 $ESs$ 来避免死锁。这样，不仅可以大大提高FMS预测死锁标记的效率，而且在保证FMS稳定运行的同时，尽可能降低运行成本。