Frey, G.: Programmable Logic Controllers. Book section, 5p, 2014, ; in: Baillieul, J.; Samad, T. (Eds.): Encyclopedia of Systems and Control. ISBN 978-1-4471-5102-9 (online), Springer-Verlag London, United Kingdom, 2015. 


Since the 1970s, the programmable logic controller (PLC) has been the primary workhorse of industrial automation. For a long time, it has provided a distinct field of research, development, and application, mainly for control engineering. This area has produced its own design methods and programming languages. Due to its importance for industrial application, a lot of these methods have been standardized by the International Electrotechnical Commission (IEC). Currently the most influential standards are IEC 61131 (John and Tiegelkamp 2010) and IEC 61499 (Vyatkin 2011). While the latter one is dedicated to distributed systems, IEC 61131 covers the PLC as such. This standard consists of several parts.