The plane landed too soon Friday and cut short my OPC story. So, here’s the conclusion:
A number of people have raised the question about OPC UA replacing PROFINET CBA (Component Based Automation). First, a reminder of what CBA is – an easy-to-use, peer-to-peer integration technique. It solves the problem of integrating best-in-class machines from different vendors (with different control equipment on them) into a single production line. This is a unique feature of PROFINET that allows peer-to-peer integration without programming, among controllers from different manufacturers, even using different fieldbuses. Some controllers have this capability built in; those that don’t can still connect using proxies. A proxy is similar to a gateway, but rather than being the product of a single vendor, it’s defined in the PROFINET spec.
To confirm my conclusion that OPC UA is not a replacement for CBA, last month in Hanover I had a conversation with Tom Burke, OPC President. OPC UA definitely provides the ability to integrate diverse controllers when integrated into those controllers. But asking it to work in 10 milliseconds is not reasonable. (I’ve used 10 milliseconds as an example here; PROFINET CBA can certainly work faster – one millisecond is not unusual.) OPC UA does not have the proxy concept for using controllers that do not natively support it. PROFINET CBA does and, in addition, it provides a framework for configuring interconnections in a graphical environment. Downloading those interconnections does not even require taking the PLC out of run mode. OPC is still in the picture with PROFINET though; OPC the only logical way to move data into a computer, be it for HMI or historian or whatever purpose.
Coordinating equipment within one production line: how do users make those interconnections today? This was the topic of an interesting side conversation in Raleigh. The one word answer: wire! Connect a wire from a digital output on vendor A’s PLC to a digital input on vendor B’s PLC. And probably not just one wire, but a bunch of wires. This is fine for binary information, but what about more complex data like tracking information? Now you have to use vendor A’s PLC programming software to create a means of communicating with vendor B’s PLC. Of course, you have to use vendor B’s PLC programming package to create the receiving end of that information. Now you can use PROFINET CBA instead. That saves a lot of time, is easier to maintain, and is more flexible when the inevitable changes occur.
I still have one more interesting topic from Raleigh to cover. I’ll get to that in a day or two. In the meantime, I’ll enjoy our early summer temperatures here in Arizona. We hadn’t broken 100 degrees since last September 21… until yesterday. Today’s temperature should break a record, topping out at a predicted 110. (But it’s a dry heat.)