基于Petri网的事件协调控制方法研究

Study of Events Collaborative Control Method Based on Petri Nets

事件的协调控制是离散事件系统中一项重要的研究内容,同时包含资源约束和事件约束的混杂约束更是系统设计的难点问题。以DES系统的加权Petri网模型为基础,以DES中变迁库所混杂约束的转换问题为研究对象,将事件协调约束转换为Petri网系统的结构约束,使得库所变迁混合约束问题转化为单一的库所约束问题。首先,提出基于Petri网的事件协调控制方法的设计算法,通过研究变迁约束转换为库所约束的规则与方法,将DES变迁库所混杂约束问题转换为单一的库所约束问题,从库所约束的角度来分析事件协调控制。其次,在3种不同系数约束的变迁≤约束表达式下,利用Petri网结构的特性,将变迁间的协调控制约束转换为系统的库所≤约束,并给出具体的算法步骤。最后,给出基于Petri网的事件协调控制方法的技术难点,剖析进一步分析和研究的主要问题。

The collaborative control method of events is an important research aspect in the area of discrete event system,while the hybrid restrictions including resource constraints and event constraints are especially difficult problems in the system construction.Based on the weighted Petri nets model of DES,and hybrid restrictions including transitions and places are taken in consideration,the event collaborative constraints are transformmed into structure constraints of the corresponding Petri net model,and then the hybrid restrictions can be transformed to place restrictions.First of all,the converting method of places and transitions hybrid restriction conditions in DES was studied,and the transition collaborative control algorithms based on Petri nets have been proposed.By structure converting of Petri nets,the hybrid restriction conditions of places and transitions of DES are converted into pure places restrictions,and the goal of studying events collaborative control from the point of pure places restrictions is realized.Secondly,under three characteristic situations that behaving different coefficient restrictions in≤restriction expression,the converting rules by structure converting of Petri nets were proposed,then the transitions≤restriction conditions were converted into places restrictions,and the converting algorithms and procedures were elaborated in detail.Finally,the key difficult problems of events collaborative control were studied,and research directions and application problems for further study were discussed.