Open Source OPC UA PubSub Over TSN for Realtime Industrial Communication

Abstract

OPC UA is a client-server communication protocol for industrial use cases without hard realtime requirements. The new PubSub extension of OPC UA adds the possibility of many-to-many communication based on the Publish / Subscribe paradigm. In conjunction with the upcoming Time-Sensitive Networking (TSN) extensions of Ethernet, OPC UA Pub Sub aims to also cover time-deterministic connectivity. This poses requirements to OPC UA implementations that have traditionally not been regarded. We propose an approach to combine non-realtime OPCUA servers with realtime OPC UA Pub Sub where both can access a shared information model without the loss of realtime guarantees for the publisher. As a result, the publisher can be run inside a (hardware-triggered) interrupt to ensure short delays and small jitter. An open source implementation of OPC UA Pub Sub is provided based on the open62541 SDK. This is also the basis for measurements used to evaluate the potential of the technology.