采用普通Petri网的自动化立体仓库系统的PLC程序设计

PLC Program Design for Automated Storage and Retrieval Systems Based on Ordinary Petri Nets

以一个实际立体仓库系统的出库流程为例,给出利用普通Petri网设计其可编程逻辑控制器(PLC)程序的方法.首先,根据自动化立体仓库系统的出库流程,提出其对象Petri网的设计方法;然后,根据系统工艺流程对应的顺序控制规范,在对象Petri网的基础上增加执行机构的变迁,最终得到闭合Petri网(监控器);最后,给出将闭合Petri网转化成PLC梯形图的方法,实现自动化立体仓库系统的形式化建模和PLC程序设计.研究结果表明:所提出的设计方法更容易自动实现系统的控制器设计及转化为梯形图语言.

Taking an actual automated storage and retrieval system＇s outbound process as an example, an approach is proposed to design its PLC program using ordinary Petri nets （PN）. First, the method is proposed to model an automated storage and retrieval system as a plant PN based on its outbound process. Then, according to the control objective of the correct execution sequence, the closed-loop PN （supervisor） is obtained by adding the arcs of actuators into the plant PN. Lastly, the method is proposed to translate a closed-loop PN into a ladder diagram, and consequently, the formal modeling and PLC program design for an automated storage and retrieval system are implemented. The research results show that the proposed methods are easier to realize the design of controllers and transformation of ladder diagram.