The foundational reasons for employing industrial Ethernet to enable Industry 4.0 are well known: They create enterprise-wide transparency, ease data access, and provide standardized interfaces with broadly familiar mechanisms.
Though it might be popular to dismiss phrases like “enable Industry 4.0,” which I used above, it’s important to understand that this is not just some flippant turn of phrase. Sure, it might have once seemed that such phrases were just different words for what we’ve been trying to do all along. But it’s becoming increasingly clear that something more is happening—and it appears that a convergence of information technology (IT) and operational technology (OT) networks is the key.
But what does it all really mean? From a classic ISA95 perspective, it means that the field level and the manufacturing execution system (MES) level are getting closer.
In the traditional ISA95 model, industrial Ethernet plays a role only at the lowest level (OT) in the field. From there, it connects to the controls level, which then interfaces to an MES (IT), with the primary goal being to run the plant. With Industry 4.0 and the Industrial Internet of Things (IIoT) entering the scene, however, the boundaries between these levels are blurring. As a result, the relationship between the field level and the MES level is set to expand.
The role of OEE
Achieving maximum overall equipment effectiveness (OEE) is the primary goal of any MES, and it’s where an expanded relationship directly with the field level via industrial Ethernet can help. By definition, OEE is the product of three variables: availability (A), performance (P) and quality (Q). As such, A x P x Q = OEE.
High availability (A) correlates directly to uptime. Among other things, it means shortening downtime, if not eliminating it altogether. Through comprehensive diagnostics, an industrial Ethernet such as Profinet can pinpoint unplanned errors by providing complete what/who/where/when/how information. This can be made available in common control-level components such as programmable logic controllers (PLCs), human-machine interfaces (HMIs) or supervisory control and data acquisition (SCADA) systems. Since Profinet can use TCP/IP for diagnostic messages, this information can be programmed to be made available wherever required. In fact, these methods are nothing new on the OT side.
So how can we take a step forward in terms of diagnostics in the context of Industry 4.0? The answer is OPC UA. Currently, within Profibus/Profinet International (PI), we are working diligently on a companion specification between Profinet and OPC UA. One of the first areas of our focus is on diagnostics. By mapping Profinet diagnostic data to OPC UA, this information can more easily be consumed by IT software packages like MES. Such standardized information flow should ultimately help minimize unplanned downtime.
As far as performance (P) is concerned, the path is clear: Run production at the rate that maximizes throughput. For Profinet, network speed and determinism have always been priorities. Like anything, throughput itself is a complex equation, and network performance is just one part. But maintaining an open network infrastructure while simultaneously providing high performance is nothing new.
So how can we take a step further in terms of network performance in the context of converged IT/OT networks? The answer is Time-Sensitive Networking (TSN). The techniques that have allowed Profinet networks to be both high-performing and open since the early 2000s are now becoming IEEE Ethernet standards. Eventually, TSN will become the first layer in the foundation of a converged IT/OT network. And since Profinet is based on standard unmodified Ethernet, as TSN becomes integrated into Ethernet itself, those features will be inherent.
The combination of Profinet and OPC UA plus TSN provides a recipe for success in the growing relationship between the conventional ISA95’s field and MES levels. This is particularly true under the growing pressures of Industry 4.0 and you can see it happening already today as field devices with OPC UA capabilities are being introduced into the market. These devices provide the communication means for direct information flow to the MES level.
Of course, all these developments mean that industrial Ethernet resources will be taxed as a result of increased non-control-related network traffic. However, TSN will help ensure that the primary purpose of an industrial Ethernet network (i.e., controlling the plant via an industrial Ethernet protocol such as Profinet) will remain unaffected while allowing it to do even more in the future.
For more information, visit PI North America at us.profinet.com.
