Modeling and Race Detection of Ladder Diagrams via Ordinary Petri Nets
提出用普通Petri网对PLC程序建模，并通过可达图技术检测、定位和修正程序中的竞争问题，附有实例说明。
This paper presents an ordinary Petri net (PN)-based approach to the modeling and race-detection problems of programs for programmable logic controllers (PLCs). First, a PLC program is formalized by a graph where nodes represent contacts and coils. Second, an algorithm is proposed to translate this graph into an ordinary PN. Third, a method is presented to detect whether there exists a race in a program by using a reachability graph technique, to locate a race by introducing the race path, and to correct a race by analyzing the subnet that contains it. An example is utilized to illustrate the theoretic results.