For resolving the question of complexity and indigestibility in programming the sequential control by the basal logistic instruction of PLC,making use of the SFC of PLC to program is a effective method.This paper takes Siemens S7-200 PLC as example,by automatic materials car control.It leads to sequential function chart,then through a specific example,using sequential function chart method to design its control procedures.From the result of programming and comparing and the method of basal logistic instruction,we can see that this method is simple,direct and logic and it improves the efficiency of the design of programming.%针对PLC的基本逻辑指令编写顺序控制程序时所存在的编程复杂、不易理解等问题,采用顺序功能图是一种非常有效的方法。以西门子S7-200系列PLC为例,由自动送料小车的控制引出顺序功能图,再通过具体实例,采用顺序功能图的方法编写其控制程序。从编程结果看,与应用PLC的基本逻辑指令方法相比具有简单、直观、逻辑性强等特点,提高了编程的效率。
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