Assessing Open Interfaces and Protocols of PLCs for Computation Offloading at Field Level

TL;DR

This paper evaluates the open communication interfaces of Siemens S7 PLCs to determine their suitability for computation offloading in Industry 4.0, focusing on plug & play capability, metadata support, protocol efficiency, and performance.

Contribution

It provides a detailed analysis of PLC communication interfaces, highlighting their potential and limitations for integration into modern offloading systems.

Findings

Interfaces vary in plug & play capability

Metadata support is inconsistent across interfaces

Performance metrics show different update times

Abstract

Programmable logic controllers (PLCs) are the core element of industrial plants in todays deployments. They read sensor values, execute control algorithms, and write output values. Furthermore, industrial plants have lifetimes of one or more decades. Thus, in a realistic Industry 4.0 scenario, these devices have to be integrated in novel systems. In order to apply advanced concepts and technologies, such as computation offloading, which requires data exchange between PLCs and edge cloud, we investigate open communication interfaces of two typical PLCs of Siemens S7 series. Hence, each of the interfaces is analyzed based on plug & play capability, if metadata is provided, protocol efficiency, and performance. For the latter, the smallest possible update time for each of the interfaces will be measured.