提出一种新的死锁控制策略,保证含有并发执行装配过程的一类柔性制造系统(Flexible manufacturing system,FMS)G—system的非阻塞性,即布控制下,受控系统从任意可达状态都可到达理想状态.首先对Petri网模型运用混合整数规划算法求取一个最大的死信标,然后从最大的死信标中求取一个需要受控的极小信标,并对其添加控制库所,从而保证所有信标的最大可控.和现有方法相比,该策略避免了求取所有的信标,且添加较少的控制库所即可获得结构简单、许可行为趋于最优的控制器.
Developed in this paper is a novel deadlock control policy that can ensure concurrent execution of manufacturing assembly processes in flexible manufacturing systems (FMS) through a class of nets, called G-system that is a large class of discrete event systems. A relevant property of the system behavior is to be non-blocking, i.e., from any reachable state, a desirable state can be always reached under supervision. First, a maximal deadly siphon can be obtained by using the mixed integer programming technique, and a monitor is added to a minimal siphon that needs to be controlled, which is derived from the maximal deadly siphon in order to ensure the controllability of all siphons of Petri nets. Compared with the existing policies, the advantage of the proposed approach is that complete siphon enumeration is avoided and a much smaller number of monitors are added, which result in obtaining a simple supervisor with suboptimal permissive behavior.