Rethinking PLCs: Industrial Ethernet for Large-Scale Real-Time Distributed Control Applications
Birgit Plötzeneder, Pavel Bastl, Ondrej Janda, Alexej Kru¿enko, Jiří Trdlička · JACOW · 2019
Many research facilities rely on PLCs to automate large slow systems like vacuum or HVAC, where price, availability and reliability matter. The dominant architecture consists of local units of controllers/ modules (programmed in IEC61131-3 languages), which operate mostly autonomously from a SCADA layer. While some vendors provide low-level stacks to encourage growth of their ecosystems, PLC programming remains largely within a closed, proprietary world. In this paper, we introduce a different way of thinking about PLC hardware. Working with the open stacks intended for the design of new EtherCAT (Beckhoff) / Powerlink (B) modules, we built an abstract C+± API to control the existing ones. These industrial ethernet busses can be propagated using standard network hardware, so any RT-Linux system can now control any PLC module from anywhere in our facility using high-level languages (C++, LabVIEW). This way, PLC modules are seamlessly integrated into our distributed TANGO-based control system. PC-PLC interfaces are no longer needed; or in the case of traditionally implemented subsystems (machine safety), trivial.