Safe PLC Controller Implementation IEC 61131-3 Compliant based on a Simple SAT Solver: Application to Manufacturing Systems

Abstract

In this study, manufacturing systems are considered as Discrete Event Systems (DES) with logical Inputs (sensors) and logical Outputs (actuators). In previous work, an original implementation of safe controllers (using safety logical constraints) for manufacturing systems, based on the use of a CSP (constraint satisfaction problem) solver, was proposed. However, the proposed solution was not IEC 61131-3 compliant. In other words, it was not possible to implement it in a PLC (Programmable Logic Controller). In this paper, a proof of concept IEC 61131-3 compliant has been carried out. To perform this challenge, an original simple CSP -SAT solver in ST (Structured Text) has been developed and programmed. The algorithm has been tested and validated by using a M340 Schneider Electric PLC and a box sorting simulated process using the FACTORY I/O software from the Real Games Company (www.realgames.co). It seems to be the first time that a SAT solver developed for PLC, is used in real time as a part of a PLC program to get a safe controller.