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OEMs and system integrators have high hopes for OPC UA TSN. So far, those hopes have been based on theoretical concepts and technologies still under development – but not any longer. Together with its partner companies, B&R has proven the ability of OPC UA TSN to meet communication requirements from the line level up to the ERP level under real-world conditions.

Over the past few months, B&R has performed intensive field testing together with TSN network specialist TTTech. "The results are impressive," reports B&R's marketing manager Stefan Schönegger. "In some aspects, OPC UA TSN has even outperformed our expectations."

Time-critical applications at the line level, such as synchronization of conveyor belts with various other equipment, require cycle times as low as two milliseconds. "We've gone even lower than that on our test installations," says Schönegger. With jitter measurements as low as 100 nanoseconds, the results were on par with the best fieldbus systems on the market today.

Networks without borders

"The other impressive thing about our test installations is their stability," emphasizes Schönegger. "After all, we're working with technology so new that its IEEE specification hasn't even been completed yet." B&R's test installations will soon join those of other participants in the IIC's TSN Testbed to examine the interoperability of components on a multi-vendor OPC UA network with TSN. Other TSN Testbed participants included: National Instruments, Cisco, Schneider, Bosch, GE, KUKA, Intel and TTTech.

Low resource intensity

Pivotal criteria for practical OPC UA applications will be its code size and resource requirements. "If OPC UA were only able to run on powerful industrial PCs and controllers, use in machinery and equipment would be out of the question," explains Schönegger. By implementing OPC UA on a bus controller from its X20 system, B&R has clearly demonstrated the feasibility of I/O-level applications for OPC UA servers and clients. "It proves that OPC UA is perfectly scalable to any conceivable task at the line-level and beyond."

"OPC UA TSN has even outperformed our expectations in some aspects."Stefan Schönegger, Marketing Manager, B&R

Reduced network traffic

With its bus controller implementation, B&R has also tested an important new feature of the OPC UA specification. The publish-subscribe (pub/sub) model plays a key role in allowing OPC UA TSN to achieve the necessary performance.

Until now, OPC UA has used a client/server mechanism, where a client requests information and receives a response from a server. On networks with large numbers of nodes, traffic increases disproportionately and impairs the performance of the system.

The publish-subscribe model, in contrast, enables one-to-many and many-to-many communication. A server sends its data to the network (publish) and every client can receive this data (subscribe). This eliminates the need for a permanent connection between client and server, which is particularly resource intensive.

B&R is actively participating in the OPC Foundation working group developing the specification for OPC UA's publish-subscribe model. "I expect the specification to be completed by the end of the year – and rapidly implemented by many manufacturers soon thereafter," says Schönegger.

With a client-server mechanism, a client requests information and receives a response from a server.
With a publish-subscribe model, a server sends its data to the network (publish) and every client can receive this data (subscribe).

OPC UA as a standard

The momentum behind the OPC UA movement is evident in the number of standards organizations basing their work on the vendor-independent protocol. EUROMAP, the leading developer of global standards for the plastics industry, recently defined OPC UA as the basis for two new EUROMAP interfaces, and more are on the way.

The umbrella organization for the packaging industry, OMAC, will also be integrating OPC UA into its PackML standard and is already working on specific implementations. "It really is astonishing how quickly such well-established industry standards are now turning to OPC UA," says Schönegger. "The performance demonstrated by our field testing with OPC UA TSN confirms that they're moving in the right direction."

For more information on the topic of OPC UA, see OPC UA.

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