There has been a lot in the automation press and online about using OPC UA over Time Sensitive Networks. The resulting OPC UA TSN certainly could be the basis for a vendor independent real-time Industrial Ethernet, but will it happen?
Over the years there have been many opportunities to unify industrial fieldbus networks. Most recently the introduction of Ethernet to factory automation networks. Based on the computer industry, the hope was for plug-and-play industrial hardware communicating over Ethernet, but three things happened.
Firstly, the hardware manufacturers realised standard Ethernet would not provide the determinism needed for some factory automation applications. Secondly, moving to an open architecture meant it would be easier for users to switch hardware to other brands. And finally, several smaller automation producers developed their own Industrial Ethernets developed based on good ideas and technologies.
The result was a plethora of deterministic, proprietary networks that manufacturers have been promoting as ‘open’ networking standards. Sadly, most of these are incompatible with each other.
However, sanity may be returning to the market by bringing together two separate technologies, OPC (Open Platform Communications) UA (Unified Architecture) and Time Sensitive Networks (TSN). Importantly, the resulting OPC UA/TSN is not another new Industrial Ethernet. It is a non-proprietary technical solution for providing high performance deterministic communication between industrial devices to field level over Ethernet.
OPC UA is Platform Independent
OPC is an interoperability standard providing secure and reliable data exchange in industrial automation and related industries. It specifies the communication of real-time plant data between control devices from different manufacturers. OPC is platform independent and ensures the seamless flow of information among devices from multiple vendors. It was originally developed from Microsoft Windows in 1966, but is now managed by The OPC Foundation.
Developed more recently by the same organiation, OPC Unified Architecture (OPC UA) is different. OPC UA has moved away from being a Windows based platform, to be platform-independent. It combines the functionality of the existing OPC interfaces with new technologies such as XML and Web Services to deliver higher level MES and ERP support. This allows OPC UA to share multivendor converged network infrastructures with other applications including the existing and updated Industrial Ethernet solutions.
Time Sensitive Networks
TSN is being developed by the IEEE, and the goal is a profile for industrial automation standardised by the IEC/IEEE 60802 committee. Their aim is to provide deterministic services through IEEE 802 networks. This means guaranteed packet transport with bounded latency, low packet delay variation, and low packet loss.
OPC UA TSN
According to the ARC Advisory Group, under Industry 4.0, the amount of data generated at the machine level is growing exponentially. This requires capable network architectures, and OPC UA TSN is emerging as an excellent solution for real-time. By offering vendor independent Ethernet communication for industrial manufacturing, it addresses real-time functionality and data communications for production and process. Furthermore it could simplify automation architectures as the current master-slave and peer-to-peer arrangements will become obsolete.
In a follow up to the 2018 Hannover Fair, Bill Lydon of Automation.com believes TSN for industrial automation has potential to be a unifying network but has a level of complexity that could have a negative impact on network reliability. Furthermore, the cost of applying TSN could be significant as ethernet switches are more expensive with the added TSN capabilities.
Combining these technologies, could provide the opportunity for a genuine vendor independent real-time Industrial Ethernet. Markedly, all the major automation equipment manufacturers are planning to integrate it in their Ethernet products. Companies actively cooperating include, Siemens, Rockwell, Schneider, Mitsubishi.
They are not acting in unison, but rather alongside other device makers as an ad hoc group. It is not clear whether they are developing products for multi-vendor control, or simply to integrate OPC UA/TSN into their own solutions.
