An expert describes ways standard software stacks for the industrial Internet of Things can be integrated in modern automation systems.
Integration is an increasing challenge in large, industrial systems. In the past, industrial system integration focused on devices, networks and other hardware – the physical layer. Software was configured and contained within specific devices for the most part.
With the industrial Internet of Things (IIoT) and its ubiquitous network connectivity and virtualization, the system integration challenge now includes the software that runs on the physical layer. As Marc Andreeson famously said, “Software is eating the world.”
DDS is an IIoT connectivity standard that specifically addresses the growing software integration challenges in industrial systems. For example, DDS is used in oil rig automation platforms. These platforms have been developed to greatly streamline the well-drilling process by integrating all the subsystems on the rig and using software to drive the drilling process.
Automation platforms require an increasing amount of distributed software at the control and process levels. Once a technician monitored and controlled the mud pump subsystem on the rig and coordinated with other technicians running other subsystems like the drill head. With an automation platform, there are compute nodes running software applications that manage both subsystems.
These applications need to share data at high rates between dozens to hundreds of software applications in ways that are secure and can scale. This is where the use of DDS, one of the core IIoT connectivity standards suggested by the Industrial Internet Consortium (IIC), has proven its value.
OPC UA is another IIC core connectivity standard in industrial automation used to address the device integration challenge. OPC UA simplifies the configuration of devices and controllers that need to be connected in manufacturing systems. It also provides the information models (like MTConnext for machine tools) that help address semantic interoperability between applications and devices.
Future industrial automation systems across process control, building automation, oil rig automation and more will be integrated at both the software and device level. It makes sense to integrate DDS and OPC UA to support these needs.
One integration approach is to use OPC UA-DDS gateways based on standards of the Object Management Group. DDS plays the role of a core bus, streamlining the integration of distributed software applications and the sharing of data and service invocations between them.
OPC UA devices and applications are bridged to the DDS databus using the newly standardized OPC UA-DDS Gateway. With this approach, software-intensive industrial automation systems with OPC UA devices and applications can be integrated at both the software and device levels.
In the future, it may make sense to use a tighter integration that brings the best of both DDS and OPC UA together by combining OPC UA’s client-server model and domain information models with DDS’s proven publish-subscribe technique. This approach provides an API layer above DDS and OPC UA to better address integration challenges.
An alternative approach described in a white paper online merges the OPC UA object-oriented model with the DDS data-centric, publish-subscribe model. It will scale to thousands of nodes, eliminate dependence on servers, provide flexible physical-layer implementation and enable fine-grained security.
Which of these two integration approaches makes sense for a specific industrial system depends on use cases and overall system requirements. In fact, these two approaches can be used in the same system as needed. Regardless, combining the software-integration strength of DDS with the device-integration strength of OPC UA is a promising path forward.
-- Brett Murphy is the senior director of market development for the industrial Internet of Things at Real-Time Innovations (RTI).