DISCRETE EVENT CONTROL METHODS: A REVIEW

摘要

Programmable logic controllers or more generally microprocessor/computer based controllers have played a significant role in advancing industrial automation. A majority of them are designed and implemented with relay ladder logic (RLL) programming. Recently new methods are emerging with the objectives to handle large industrial automation projects and improve understandability, flexibility, and maintainability of the resulting design. This paper overviews and evaluates these approaches through a level control process example. Among them are: direct implementation of RLL, logic diagrams, timing/sequence diagrams, state diagrams, Petri nets, and sequential function charts. Their major advantages and disadvantages are indicated.