Deadlock resolution has been an important research topic in the field of automated manufacturing systems (AMSs). Researchers generally assume that AMS resources never break down whereas only a few resolve the issues of resource failures in the discrete-event supervision of AMSs. In fact, an AMS consists of a number of numerically controlled machines interacting with each other. The failure of resources happens unexpectedly. In this article, we allow parallel routes to use unreliable resources. Because of their powerful modeling capabilities, Petri nets are used to model the considered AMSs. By using a look-ahead control strategy, a robust supervisory control policy is developed for AMSs with assembly operations allowing resource failures. Our objective is to advance parts requiring failed resources in their remaining routes into a special position so as to release shared resources in case some unreliable resources fail. Consequently, those parts not necessarily requiring any failed resource can keep progressing all the time. The conventional methods are on the basis of monolithic and structure-oriented control specifications with centralized supervisors. Our policy can be implemented in a distributed, online, and local way. Several examples are given to elucidate our control policy clearly. Note to Practitioners-In automated manufacturing systems (AMSs), resources such as machines and tools with higher reliablity are always expensive. Sometimes, when it is not cost-effective to use resources with higher reliability, manufacturers may choose some resources with possible failures. These resources are thus considered as unreliable ones in our article. Normally, unreliable resources may fail unexpectedly. Their occurrences can lead a system to stagnation, causing unnecessary downtime, and bringing economic loss to enterprises. To resolve such stagnation issues, we develop a robust supervisory control policy to synthesize a robust liveness-enforcing supervisor for AMSs with assembly operations and unreliable resources. The supervisor can guarantee that a controlled system continues to progress without deadlock and blocking states even if some unreliable resources fail to work.

中文翻译：

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使用 Petri 网进行装配操作的自动化制造系统的鲁棒死锁避免和控制


死锁解决一直是自动化制造系统（AMS）领域的一个重要研究课题。研究人员普遍认为 AMS 资源永远不会发生故障，但只有少数解决了 AMS 离散事件监控中的资源故障问题。事实上，AMS 由许多相互交互的数控机器组成。资源故障会意外发生。在本文中，我们允许并行路由使用不可靠的资源。由于其强大的建模能力，Petri 网被用来对所考虑的 AMS 进行建模。通过使用前瞻控制策略，为具有允许资源故障的装配操作的 AMS 开发了强大的监督控制策略。我们的目标是将剩余路线中需要故障资源的部分提前到一个特殊的位置，以便在一些不可靠的资源发生故障时释放共享资源。因此，那些不一定需要任何失败资源的部分可以一直保持进展。传统的方法是基于具有集中监控器的单片和面向结构的控制规范。我们的政策可以以分布式、在线、本地的方式实施。举几个例子来清楚地阐明我们的控制政策。从业者注意——在自动化制造系统（AMS）中，可靠性较高的机器和工具等资源总是昂贵的。有时，当使用可靠性较高的资源并不划算时，制造商可能会选择一些可能出现故障的资源。因此，这些资源在我们的文章中被认为是不可靠的。通常，不可靠的资源可能会意外失败。 它们的出现会导致系统停滞，造成不必要的停机，给企业带来经济损失。为了解决此类停滞问题，我们开发了一个强大的监督控制策略，为具有组装操作和不可靠资源的 AMS 综合一个强大的活性执行监督器。即使某些不可靠的资源无法工作，主管也可以保证受控系统继续前进，而不会出现死锁和阻塞状态。