Wu Naiqi, Zhou MengChu
Department of Mechatronics Engineering, Guangdong University of Technology, Guangzhou, China.
IEEE Trans Syst Man Cybern B Cybern. 2005 Dec;35(6):1193-202. doi: 10.1109/tsmcb.2005.850141.
An automated manufacturing system (AMS) contains a number of versatile machines (or workstations), buffers, an automated material handling system (MHS), and is computer-controlled. An effective and flexible alternative for implementing MHS is to use automated guided vehicle (AGV) system. The deadlock issue in AMS is very important in its operation and has extensively been studied. The deadlock problems were separately treated for parts in production and transportation and many techniques were developed for each problem. However, such treatment does not take the advantage of the flexibility offered by multiple AGVs. In general, it is intractable to obtain maximally permissive control policy for either problem. Instead, this paper investigates these two problems in an integrated way. First we model an AGV system and part processing processes by resource-oriented Petri nets, respectively. Then the two models are integrated by using macro transitions. Based on the combined model, a novel control policy for deadlock avoidance is proposed. It is shown to be maximally permissive with computational complexity of O (n2) where n is the number of machines in AMS if the complexity for controlling the part transportation by AGVs is not considered. Thus, the complexity of deadlock avoidance for the whole system is bounded by the complexity in controlling the AGV system. An illustrative example shows its application and power.
自动化制造系统（AMS）包含许多通用机器（或工作站）、缓冲区、自动化物料搬运系统（MHS），并且由计算机控制。实现MHS的一种有效且灵活的替代方案是使用自动导引车（AGV）系统。AMS中的死锁问题在其运行中非常重要，并且已经得到了广泛研究。针对生产和运输中的零件分别处理死锁问题，并且针对每个问题开发了许多技术。然而，这种处理方式没有利用多个AGV提供的灵活性。一般来说，为任何一个问题获得最大允许控制策略都是棘手的。相反，本文以综合方式研究这两个问题。首先，我们分别用面向资源的Petri网对AGV系统和零件加工过程进行建模。然后，通过使用宏转换将这两个模型集成。基于组合模型，提出了一种新颖的死锁避免控制策略。如果不考虑通过AGV控制零件运输的复杂性，对于具有O(n2)计算复杂度的AMS，其中n是机器数量，该策略被证明是最大允许的。因此，整个系统死锁避免的复杂性受AGV系统控制复杂性的限制。一个示例说明了它的应用和功效。
