Evaluation of PLC4X based Middleware as Integrator of Brownfield systems into Industrial Cyber-Physical Systems

The emergence of the Internet of Things (IoT) and Cyber-Physical Systems (CPS), supported by the rapid growth in computing and communication technologies in the past decade, has started the fourth industrial revolution (Industry 4.0). Industry 4.0 reinvents the industrial communication paradigm by proposing a mesh of intertwined physical and digital entities, namely the digital twin network. Integration of brownfield legacy systems into an Industry 4.0 compliant CPS, due to their relatively high vendor dependency and technological heterogeneity, remains one of the biggest challenges. To tackle this issue, Open Platform Communication Unified Architecture (OPC UA) was developed. OPC UA acts as a vendor and protocol-agnostic communication middleware for data acquisition. Modern Programmable Logic Controllers (PLC) allow running an OPC UA server inside them and data access can be performed through any OPC UA client tool. While this does solve the brownfield integration problem to a certain extent, the majority of the tools on the shop floor still use vendor-specific technologies. PLC4X is a set of libraries for communicating with PLCs and fetching data from them. It supports a wide range of communication protocols and could be a promising candidate for addressing the integration challenges. Therefore, in this paper, we evaluate the viability of PLC4X as an enabler for a communication middleware that tackles the integration challenges concerning the brownfield systems in Industry 4.0.