SAVAGE, Minnesota, December 11, 2014 – With the combination of IEC 61131-3 functions and secure OPC UA communication, Beckhoff Automation offers an “SOA (Service Oriented Architecture) PLC” for more efficient, data-consistent, secure, and standardized communication for the implementation of “Smart Factories”. Industry 4.0 and Internet of Things (IoT) concepts for fast, streamlined production depend upon capable networking and communication technologies. This requires services to communicate with each other directly, and products to control themselves, instead of “top-down” communication from the ERP system via MES, PLC, and ultimately down to the sensor.
Measuring devices, sensors, RFID chips, PLCs, and other embedded systems provide important data for production in industrial applications. In conventional control architectures, data requests are initiated either cyclically or are event-triggered, always in response to requests “from above”, i.e. from the client level. The lower level always acts as a server and responds accordingly. In other words, an RFID reader or PLC controller are not “intelligent” in terms of communication. In the Smart Factory, physical, real systems and virtual, digital data merge to form intelligent, self-organizing production units. They acquire the data needed for this purpose autonomously. This means that all devices and services must be able to communicate with each other independently, irrespective of the manufacturer, operating system, hierarchy, or topology.
Beckhoff has integrated the OPC UA client function blocks, which are standardized by PLCopen in cooperation with the OPC Foundation, in the PLC. Beckhoff first proposed this initiative in 2006, and has chaired the group since 2009. The specification for the function blocks was released in 2014. As an OPC UA client, the controller can play the active, leading part, in addition or as an alternative to the conventional role allocation. The PLC is thus able to exchange complex data structures horizontally with other controllers, or it can vertically call methods in an MES/ERP system via an OPC UA server, e.g. to retrieve new production orders or write data to the cloud. This enables the production line to become autonomously active. In combination with integrated OPC UA security, this is a key step in the movement towards Industry 4.0.
At present, data exchange between the MES level and the PLC usually takes place via a time-consuming handshake procedure: The MES system signals the transfer of a recipe to the controller, for example, and the PLC acknowledges readiness. Once the recipe data have been transferred, the transfer is acknowledged. The SOA-PLC now makes it possible to transfer data to the controller with a single communication: Data values are no longer exchanged in multiple transactions, but instead handled as a single service with input parameters (the recipe) and output parameters (acknowledgement by the PLC).
“Via OPC UA we make the Remote Procedure Call (RPC) available right down to the programmed PLC function,” explains Stefan Hoppe, TwinCAT Product Manager at Beckhoff Automation. “This will significantly shorten the communication round-trip times between the PLC and MES systems and can lead to higher production throughput. It will reduce the engineering costs for establishing a data link between the shop floor and the top floor quite dramatically.”
The implementation is very simple for PLC programmers: A PLC method (with any input/output parameters) is simply available as a service call in the OPC UA server, which is integrated in the PLC. Each OPC UA client can call this service with the IT security functions and authorization integrated in OPC UA while preserving data consistency, irrespective of the operating system. The calls to the PLC can also be initiated from other devices or services at the IT level or the cloud.
Some Beckhoff customers have already implemented their first pilot projects. For example, around 560 Beckhoff Embedded PCs control pumps and water towers in the water treatment plant for the Vogtland region in Germany, which covers an area of 1,400 km². They act with distributed intelligence to make decisions independently and exchange information with each other or query statuses and process values for their own processes, in order to ensure uninterrupted process flow.
“Through the combination of IEC 61131-3 functions and OPC UA services, Beckhoff offers an ‘SOA-PLC’ for efficient, data-consistent, secure, and standardized communication. Calls to the PLC can be initiated from other devices or from services at the IT level or the cloud via remote procedure calls.”