The future of industrial Ethernet unfolds at ISA conference in Houston
On Dec. 6, the ISA hosted the Industrial Ethernet conference in Houston. As one of the nine speakers at the event, I had the opportunity to do eight times as much listening as talking. The information was excellent, and as the day progressed, the true direction of Ethernet on the factory floor became apparent.
At first glance it may appear that the move towards Industrial Ethernet is because it's cheap, universal, and open. This is somewhat true, but a closer look shows that, more than anything, management level business information requirements, i.e. ERP and MIS systems, are the real driving forces.
In terms of using Ethernet as an I/O fieldbus, Bob Lounsbury of Rockwell Automation described his research into the physical requirements of cabling and connectors. In examining temperature range, noise rejection, and physical robustness, it became apparent that in many cases, commercial off the shelf Ethernet cables, connectors and cards are not up to the task, and industrialized hardware is often necessary.
Another requirement is that application level protocols be defined. There are four clear contenders:
- Modbus/TCP, which is the venerable Modbus protocol in TCP/IP packets.
- Ethernet/IP, which is the ControlNet/DeviceNet objects on TCP/IP.
- Foundation Fieldbus High Speed Ethernet, which bundles the Foundation Fieldbus H1 protocol with OPC, XML, and Simple Object Access Protocol on TCP/IP.
- ProfiNet, which bundles the Profibus protocol with XML based OPC objects and an Open Source software model.
All of the above except Modbus/TCP were represented by their originating companies and organizations: Dave VanGompel of Rockwell, Lee Neitzel of Fisher-Rosemount, and Horst Kolbert of Siemens, respectively. Interestingly, Modbus/TCP is the only solution of the four that is well supported right now by numerous vendors on the open market. The others should see product introductions early next year.
Ken Crater of Control.com gave an excellent summary of the meaning of all those Internet acronyms like TCP/IP, UDP, NTP, SMTP, etc. And Eric Byres of the British Columbia Institute of Technology presented a fact/fiction list on Ethernet on the factory floor:
Ethernet myths:
- Ethernet won't work in factories because it's not deterministic.
- Ethernet conveniently connects every single device and computer to the same network and the Internet.
- Ethernet solves all interoperability problems.
- Ethernet design/installation is very simple.
Ethernet reality:
- Ethernet can be sufficiently deterministic, using switches to guarantee device bandwidth.
- You should never put control devices and office computers on the same network.
- Ethernet introduces numerous interoperability and integration issues.
- Ethernet design/installation must be carefully planned and executed.
Lynn Linse of Lantronix (Irvine, CA) delivered interesting information on connecting legacy equipment to Ethernet. Some key points to consider:
- It is rarely economical to "rip out" legacy wiring and systems in order to replace them with Ethernet equivalents.
- It is possible to use "COM tunneling" to package serial protocols in TCP/IP and collect non-real time data from control devices without using data concentrators.
- Ethernet is frequently expected to be a "cure all" when in fact it can open a Pandora's box of interoperability and functionality issues.
Mark Mullins of Fluke Corporation gave an enlightening talk on trouble shooting Ethernet, and described various software/hardware tools that are available for this task. Highlights included:
- Involvement and support by company management in network preparation and planning is vital to the successful implementation of networks.
- Prevention and Early Detection strategies are the most successful maintenance precautions.
- Companies who are least satisfied with their networks often have the largest number of staff maintaining them – the culprit is poor overall strategy.
- Dedicated and PC based Ethernet analyzers are available, which bring various levels of ease and sophistication to the trouble shooting process.
I covered the commercial issues of buying open solutions in a competitive marketplace, including the some interesting "rules" of the customer/vendor relationship:
- Ethernet, being only a transport mechanism, opens many "open architecture" interoperability issues.
- "Open" is not a black and white term; it is a continuum that can mean anything from "widely used but really proprietary" to "Open Source" and public domain.
- In open systems, there is always a struggle between having multiple vendors to choose from, and being able to get those vendors to guarantee that the various devices will interoperate.
- Inexperienced users can get the most from open systems by enlisting the help of a skilled systems integrator, who can select "best of class" components from multiple vendors and put them together.
Finally, a note on fieldbuses: It was very clear that while Ethernet is gradually taking its place as a fieldbus, it was equally clear Ethernet will not replace other fieldbuses in some applications. For example, it's highly doubtful that Ethernet would be a good choice for devices on a robotic welder (high electrical noise is a serious problem there) or for connecting devices which are distributed every 50 ft on a 1000-ft conveyor (Ethernet's star topology greatly limits its usefulness in this application).
A more likely scenario is that Ethernet will be used as a control bus, which communicates to both sophisticated field devices and controllers (PCs and PLCs.) Most low level field devices will still be connected to networks like DeviceNet, Foundation Fieldbus H1 and Profibus, with Ethernet providing the a link, where Web applications, ERP and MES systems can selectively extract data from the Ethernet control network.
The ISA plans another Ethernet conference, March 29 in Chicago. For details, call Louise Clark at ISA: 919-990-9281.
Synergetic offers a 22 page white paper, "The Pros and Cons of Ethernet and 8 Popular Fieldbuses." To receive a copy, e-mail fieldbus@synergetic.com with your mailing address.
Perry Sink is marketing manager at Synergetic Micro Systems (Downers Grove, IL USA) which produces diagnostic tools, PC and embedded interfaces for industrial networking.