Design and Implementation of a Logic Controller using Petri Nets and Ladder Logic Diagrams

Abstract

Design methods for sequence controllers play an important role in modern industrial automation. The Programmable Logic Controller (PLC) in general meets today's automation requirements. The increasing complexity and varying needs of modern discrete industrial systems have challenged the traditional design methods such as the use of Ladder Logic Diagrams (LLDs) for PLCs. This paper presents a new method for using Petri net models in order to design and implement a sequence controller for a small scale robotic cell which consists of a robotic manipulator, a variety of sensors and electro-pneumatic actuators. The proposed method leads directly to the generation of the associated LLD and it has proved to be effective through the application to sequence control of a small-scale industrial system. In addition, it has reduced the period for developing, debugging and reengineering of the LLD, compared to the traditional method that directly prepares an LLD. Experimental results are included to show the effectiveness of the PN/LLD controller.