OPC UA: Industry 4.0 glue?

The growth of the Industrial Internet of Things (IIoT) and Industry 4.0 is driving the need for open and secure connectivity between devices. This has resulted in the OPC Foundation’s Unified Architecture – OPC UA –increasing being considered as the standard for ensuring that this can take place. Rather than replacing the standards, OPC UA complements them by creating a common layer for exchanging information. 

Freed from the need to run on a specific OS, the open data connectivity that OPC UA embodies can be offered on virtually any networked platform. It supports interoperability between a range of manufacturing processes and equipment, protecting legacy of investment for many companies. There are security benefits too – the OPC UA standard was designed from ground up with security in mind. 

However, according to Arun Anathampalayam, senior product marketing manager at Honeywell, just choosing OPC UA isn’t enough. He said: “The importance of an effective software development kit (SDK) cannot be underestimated, as it provides the means for controls suppliers to quickly and efficiently implement OPC UA into their products. With the right SDK, control suppliers can minimise their development time and effort.” 

Now more than ever, manufacturing companies need to make sense of vast quantities of data that could have a critical impact on plant performance. “As decision-makers transition towards a more connected, intelligent plant and the IIoT continues to transform the industrial manufacturing industry, the role of OPC UA will only grow in importance,” continued Anathampalayam. “The choice of SDK may not immediately be viewed by leaders as a priority, but finding one that accurately fits specific requirements will be vital in making the smooth transformation to Industry 4.0 a reality.”

The choice of SDK will depend on the objectives. Suppliers in the automation market, for example, require an effective SDK solution for deploying IIoT connectivity across their products. This must include robust, user-friendly tools that can embed OPC UA functionality into the supplier’s device or microchip quickly, so no time is lost in moving new products to market. Vendor development teams, on the other hand, will be more likely seek a fully scalable SDK that can interconnect industrial software systems, regardless of the platform, operating system, or size.

According to Thomas Hilz, business development manager at Moxa, OPC UA is the glue that integrates machines and devices from different vendors with different protocols and technologies, making the ever-increasing amounts of data manageable. For this reason Moxa was an early invester in the development of a comprehensive OPC offering for its customers, including OPC UA loggers and servers. In most remote data acquisition systems it is necessary that additional human resources collect data manually from remote storage devices to load them into a database – all of this during regular daily operation. 

“Even with RTUs remotely collecting data over the network, software is needed to convert and upload these data logs,” said Hilz. “Moxa’s MX-AOPC UA logger makes real-time data collection easier, it also simplifies the conversion of historical data into database-ready formats.” The logger interacts directly with the company’s OPC UA Server, working as a bridge between field data and stored databases or spreadsheets. Furthermore, the MX-AOPC client converts and uploads data logs to the central database. The logger can collate tags from individual Moxa RTUs or remote I/O devices into the same database or spreadsheet, freeing users from the need to manipulate data after processing.

Although, from a technical standpoint, it would certainly be feasible to add real-time capability to OPC UA itself, but doing so would involve considerable effort and would still have disadvantages. This is why many automation and robotics manufacturers have joined forces to move in a different direction and is why OPC UA will take advantage of Time Sensitive Networking (TSN).

TSN is a set of extensions that will be included in the IEEE 802.1 standard. The goal is to provide real-time data transmission over Ethernet. The TSN standard has the automotive industry behind it, so the required semiconductor components will be available very quickly and relatively inexpensively.

OEMs and system integrators have high hopes for OPC UA TSN. Until recently, these hopes have been based on theoretical concepts and technologies still under development. 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. “B&R has performed intensive field testing together with TSN network specialist TTTech. The results are impressive," said Stefan Schönegger, marketing manager at B&R. "And, in some aspects, OPC UA TSN has outperformed our expectations."

Time-critical applications at the line level, such as synchronisation 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," explained Schönegger. With jitter measurements as low as 100 nanoseconds, the results were on par with the best fieldbus systems on the market today.

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

As a founder member of the OPC Foundation, Siemens is continuing to drive the development of automation, optimising the interoperability of technologies and boosting the integration of different automation layers in the factories of our customers. According to Heinz Eisenbeiss, head of marketing factory automation, Siemens Division Digital Factory. This commitment is already bearing fruit. He said: “OPC UA is implemented in various Siemens products on all automation layers. Our industrial network products, HMIs, PLCs, RFID systems and motor management systems, for example.

“OPC UA is a standard that is particularly relevant,” continued Eisenbeiss. “With its semantic interoperability abilities it is a key element for increasing data exchange of components in factory and process automation.” Siemens was among the first companies whose products were certified. Its RFID reader, for example. “This already supports the OPC UA AutoID companion specification defined by the AIM group in which we are actively involved,” said Eisenbeiss. “This allows system integrators to save time integrating our RFID reader into the plant structure by relying on a standardised interface with clear semantics.”

On the journey towards Industry 4.0, OPC UA has played a key role for many automation suppliers, including Festo. Eberhard Klotz, Festo AG Industry 4.0 spokesperson, explains: “During the last two years OPC-UA has been installed as the key communication backbone in Festo’s latest Technology Plant in Scharnhausen, bringing machine KPI’s and energy data together with building management/infrastructure data. New machines are being constructed with OPC UA directly integrated, but even more important are retro-fit projects”. For many older machines Festo controllers are piggybacked onto the existing controls to enable them to communicate within the latest OPC-UA networks. Festo uses SAP Plant Connectivity (Pco) with OPC UA to connect the plant data to the Manufacturing Enterprise System (MES).    

Klotz continues: “OPC UA is integrated into all Festo controllers utilising CODESYS. This includes IP65 controllers which are part of the Festo decentralised installation concepts based on solenoid valve terminals, IP20 compact controllers or HMIs. Minimum integration is the server functionality, with client functionality partly offered today and for all relevant client functions in the future.”

For complete pick and place handling and gantry systems or other decentralised mechatronic motion solutions utilising electric drives, and or pneumatic actuators, Festo uses advanced diagnostic and condition monitoring concepts based on latest VDMA standard 24582 plus OPC-UA where the system is run by Festo controllers. 

This year at Hannover Messe, Festo will be implementing pilot projects with its own IoT Gateway, collecting OPC UA data from several network devices and converting them via AMQP (Advanced Message Queuing Protocol) or machine to machine connectivity protocol (MQTT) to the Festo Cloud.  App based software packages will utilise features in the connected hardware, or provide cloud-based services and analytics.

Festo Didactic also offers complete Cyber-Physical training systems on Industry 4.0, which allow OPC UA communication, plus cloud adaption to Microsoft Azure or SAP Hana.  The first such system has been recently installed at Middlesex University in the UK, where students are able to work with other Industry 4.0 technologies including augmented reality and condition monitoring.

Interesting research activity has also started on the OPC UA implementation into existing Industrial Ethernet protocols and the IO-Link association is discussing how to prepare its data format for direct integration into the OPC UA frame. Klotz concludes “We can be sure this research will proceed and can expect other interesting standards developments for example the forthcoming wireless IO link. For now, as part of the ‘Platform Industry 4.0’, OPC UA is the number-one initiative for data collection for horizontal and vertical integration of devices to the IoT.”