RELIABLE CONTAINERIZED SOFT PLCS FOR INDUSTRIAL APPLICATIONS

Sammanfattning

This study experimentally investigates whether a Soft PLC (Programmable Logic Controllers) runtime can function reliably when deployed inside a containerized environment on an industrial network device. In the context of Industry 4.0 and its ongoing digital transformation, PLCs remain a foundation of industrial automation. The Soft PLC concept, which moves control logic from dedicated hardware to software running on standardized platforms, has long been a subject of interest. Containerized Soft PLCs take this one step further by compacting the runtime within a Docker container, enabling greater portability and isolation across hardware platforms, but introduce new challenges related to timing reliability due to shared resources. Identified gaps in existing research show that limited work has evaluated the deployment of a containerized Soft PLC directly on an industrial network device from a timing reliability perspective. Using the Westermo Lynx 3510 industrial Ethernet switch as the target platform, four representative use cases were developed and evaluated, reflecting three industrial automation domains with cycle periods ranging from 1 millisecond to 10 seconds. The results show that timing behaviour varies depending on the cycle period and available resources. A minimum resource threshold was also identified, below which the system crashed and could not operate stably. Based on these findings, a jitter threshold framework is proposed as a practical guideline for stakeholders to assess whether a containerized Soft PLC solution meets their specific timing requirements. This study does not define absolute acceptance criteria. The determination belongs to the stakeholder based on their own requirements.