A Survey of IEC 61131-3 Programming Languages and Soft PLC Implementation Technologies
DOI:
https://doi.org/10.54097/3808tz64Keywords:
IEC 61131-3, Soft PLC, Programming language, Compilation, Formal verification, Real-time system, Runtime, Industrial control softwareAbstract
Programmable logic controllers (PLCs) are the core control devices of industrial automation systems. With the growing capability of general-purpose computing platforms and the increasing demand for openness and intelligence in industrial control software, soft PLC technology, which reproduces PLC functions in software on general-purpose platforms, has attracted sustained attention from both academia and industry. Taking the programming language system defined by IEC 61131-3 as the main thread, this paper systematically surveys the state of the art of soft PLC implementation technologies. First, the five standard programming languages, the differences among their execution models, and the latest evolution introduced by Edition 4 (2025) of the standard are reviewed. Second, following the two technical routes of compilation and interpretation, the evolution of language transformation research is summarized in terms of structural representation, scope of semantic preservation, and verification means; the program verification toolchain formed by K-ST formal semantics, ESBMC-PLC model checking, and the PLCverif platform is analyzed. Furthermore, the open-source ecosystems of Beremiz and OpenPLC, the commercial system landscape, and real-time implementation techniques are reviewed, with attention to emerging directions including the mainline inclusion of real-time Linux, virtualized deployment, integration with time-sensitive networking (TSN), and large language model assisted programming. Finally, the major technical challenges and development trends are outlined. The survey shows that semantic-preserving language transformation and real-time determinism of the runtime are the two core problems of soft PLC technology, that verification practice is shifting from test-based comparison toward formal verification, and that virtualization and intelligence are becoming key directions of the next stage of soft PLC evolution.
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