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"OPC UA TSN is poised to take the place of conventional fieldbus systems in Industrial IoT applications"

In OPC UA TSN, B&R sees the potential for a uniform communication standard for current and future Industrial IoT applications. That's why the automation specialist is working to develop and promote the pub/sub extension and the combination of OPC UA with Ethernet TSN. We asked Sebastian Sachse, technology manager of B&R's Open Automation business unit, what advantages OPC UA has to offer builders and operators of industrial machinery.

Sebastian, why is B&R so committed to OPC UA?

Sebastian Sachse: OPC UA is the solution to one of the greatest challenges in modern manufacturing. Whether you call it Industry 4.0, Industrial IoT or Smart Factory – the advanced manufacturing systems we envision for the future will only be possible if all the components in a production line are able to communicate over a uniform network.

Sebastian Sachse, Technology Manager - Open Automation, B&R

From individual sensors up to the ERP and DCS level, the only way to achieve the level of transparency required for Industrial IoT applications is by bridging the gap between IT and OT.

With all the different networks, fieldbus systems and communication protocols already available – why add another one?

Sachse: That's exactly the point. There are too many different protocols. On a typical plant floor, you've got machines from a variety of manufacturers, each with their own control systems and fieldbuses or Industrial Ethernet networks. Even if these machines are operating independently of one another, you're looking at added time and effort when it comes to commissioning and maintenance.

And, if you want the individual components to sync up and communicate...

Sachse: Exactly. In this scenario that would be virtually impossible. You'd need to hire expert personnel and spend time and money programming and maintaining countless gateways and interfaces. What's more, as soon as you need response times in the real-time range – to synchronize a robot with an injection press, for instance – then you're completely out of luck.

There are plenty of real-time protocols around. Why does it have to be OPC UA?

Sachse: There are a several reasons. For starters, OPC UA is an independent and widely-recognized standard that connects the worlds of production and IT. It also offers built-in security functions that ensure data is transferred securely and reliably. And then there is one very decisive difference: OPC UA transmits more than just data – it transmits information.

What does that mean?

Sachse: In OPC UA, a temperature value is not just a naked number, but rather a package of information that carries with it things like the corresponding units or setpoint limits. This makes it ideal for communication between disparate systems, because it eliminates the need for interfaces to define how to interpret values and variables. OPC UA also has what are called methods, which allow machines and components to trigger certain functions in other machines and components. This makes implementing a networked factory very easy.

But, OPC UA doesn't offer real-time capability. How do you plan to synchronize processes in real time?

Sachse: In its current form, OPC UA is fast – but in terms of automation it is neither deterministic nor cyclic. That is about to change, however.

OPC UA real time TSN2

How so?

Sachse: Through two key technologies that are being developed. First, B&R and other automation companies are working on a publish-subscribe model for OPC UA. Second, OPC UA will soon be based on Ethernet TSN.

You're going to have to explain those terms in a bit more detail. What is a publish-subscribe model?

With a publish-subscribe model, a server sends its data to the network (publish) and every client can receive this data (subscribe).

Sachse: ​​Until now, OPC UA has used a client/server mechanism, where a client requests information and receives a response from a server. With this approach, data is exchanged asynchronously and you run into problems when the network has a large number of nodes. In contrast, the publisher-subscriber model – also known simply as pub/sub – enables one-to-many and many-to-many communication. It allows developers to define a fixed time window in which the data is to be exchanged. That is a key factor when it comes to giving OPC UA real-time capability.

And what is TSN?

Sachse: TSN stands for Time Sensitive Networking. It is an extension of the IEEE 802.1 Ethernet standard to include various real-time functions. TSN allows time-critical data to be transferred deterministically, even across extensive networks. With the automotive industry driving development of TSN, the required semiconductor components will be available very quickly and relatively inexpensively.

Since we're talking about two new technologies, I imagine it will be another few years until OPC UA TSN arrives in the field.

Sachse: Not at all. The OPC UA pub/sub specification is as good as complete. We've been testing prototypes with pub/sub for some time now, including a field device. I expect the specification to be completed within a short time and rapidly implemented by many manufacturers soon thereafter. The timeline for TSN doesn't look much different. Together with the TSN Testbed of the Industrial Internet Consortium (IIC), we're currently putting the technology through its paces, and the results so far give us good reason for optimism: In some aspects, OPC UA TSN has even outperformed our expectations. I think by the end of this year we'll see the first plant where OPC UA TSN has completely supplanted the conventional fieldbus systems at the controls level – and where all communication, including up into the cloud, is handled exclusively by OPC UA.

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