An aging fieldbus system was causing too much aggravation for engineers and technicians at Radiator Specialty Co.’s Charlotte, N.C., factory. A palletizing system for containers of Gunk, Liquid Wrench and other products was often stopped when a fault on one node brought the whole system down.
Networking glitches became so common that technicians created a workaround so that many of the workers on the plant floor could restart the network.“We put a power switch on the system so equipment operators could reboot when we weren’t around,” says Shawn LaHart, control technician at Radiator Specialty. That reduced the pain and saved time, but production still remained at a halt for a couple of minutes while the system rebooted.
Late last year, the company installed an Ethernet-compatible field bus, bringing the office networking standard used in the factory down to the input/output (I/O) level. Now that Radiator Speciality has deployed Beckhoff Automation’s EtherCat protocol, the emergency power switch is getting dusty.“Our EtherCat system’s been running for months without any errors,” says Project Engineer Murray Williamson.
Radiator Specialty is one of many manufacturing companies taking Ethernet down to the fieldbus level, making the ubiquitous network look like the winner of the fieldbus wars of the mid- 1990s. It’s even being used to tackle real-time problems, as many vendors provide variations that provide determinism.
Analysts note that adoption is still low compared to the fieldbuses that have been used for years.“There are still more nodes of all other fieldbuses than of Ethernet, but it’s definitely growing pretty rapidly,” says Harry Forbes, senior analyst at ARC Advisory Group Inc., in Dedham, Mass. He notes that in 2004, there were fewer than 1 million Ethernet nodes at the fieldbus level.
However, there are a number of reasons that Ethernet’s growth in this role is expanding. Among them is that once standard Ethernet cabling—called “Cat 5” in the industry—is installed, companies are no longer tied to a fieldbus. Ethernet gives manufacturers an open environment, letting them use hardware and software from various vendors. For many engineers, that’s cause for celebration.
“Ethernet as a fieldbus has a ton of advantages,” says Ryan Becker, senior programmer analyst at Brown Printing Co., which prints many national magazines at its Waseca, Minn., headquarters. Brown is now using modules from Opto 22, of Temecula, Calif., to connect to I/O points.
Becker notes that with older fieldbuses, it is difficult to extract data for production reporting, and it’s expensive to use their specific middleware to tie into I/O points. Now, he uses Java, C or Visual Basic programming languages to access nodes. “With Ethernet I/O, I can communicate directly to I/O points at no added cost, and I can use any language I choose to tie into I/O points and extract data,” he adds.
Vendors note that the broad support for Ethernet makes it much simpler to do many common jobs. Ethernet connections and compatible software are on personal computers (PCs), and there are a number of off-the-shelf programs for many common tasks.“Now it’s relatively easy to develop and monitor software.
Every laptop has Ethernet, so you can use a Web browser as a debugging tool.There’s nothing else to buy,” says Helge Hornis, intelligent systems manager at Pepperl+Fuchs, a network component supplier based in Twinsburg, Ohio.
Another benefit is that regardless of which communication protocols are deployed, data can be transferred freely throughout the network. That means maintaining these systems can be handled efficiently even from remote locations. “Now I can monitor the whole system from my desk, I don’t have to go onto the floor and plug into a system,” says Williamson, of Radiator Speciality. He adds that he can also log in from home or from an off-site meeting.
Finding people who can do this debugging and other work is also much simpler.“The knowledge base for Ethernet is far higher than for any fieldbus,” says Benson Hougland, marketing vice president at Opto 22. This experience makes it possible to set up a fieldbus in fairly short time.The PC world’s push towards plug-and-play has made a networking technician’s job relatively simple.
“Reconfiguring the system was mostly copying and pasting. I had the whole thing done in a day,” says Radiator Speciality’s LaHart.That installation has eliminated delays from oft-occurring shutdowns, which provides a payoff that Radiator Specialty management understands and appreciates. “An hour to us is a few thousand dollars, so we’re probably looking at a few tens of thousands of dollars in extra throughput,”Williamson says.
Many users have been gaining the benefits of Ethernet field buses since roughly the start of this decade. But in applications that needed determinism, conventional fieldbuses have been the only option. However, that’s changing quickly.“There are already a number of protocols for I/O tasks that aren’t time critical. Now there are companies coming out with the speed that’s needed for determinism,” says Todd Walter, a group manager at National Instruments Corp. (NI), an Austin, Texas, automation products vendor.
A handful of networking companies are now providing variations of industrial-grade Ethernet technologies that provide realtime capabilities, going into the low milliseconds and even low microsecond times needed to assure timely delivery of message packets. This determinism now comes in many flavors. Among the available technologies are EtherCat, EtherNet/IP, Ethernet- Powerlink, the Fieldbus Foundation’s High Speed Ethernet, Modbus TCP/IP, Profinet, and SERCOS III.
Vendors note that the speed of these networks makes it possible to continue the broad thrust to integrate more functions into a single controller. Even in complex and demanding applications such as motion control, it is now possible to handle many modules from a central control panel.
“Synchronizing 100 servo axes in a microsecond is something that’s never been done before,” says Skip Hansen, I/O systems product manager at Beckhoff Automation LLC, of Burnsville, Minn. Beckhoff developed EtherCat, which is now an International Electrotechnical Commission (IEC) specification.
Hansen notes that the bandwidth of real-time Ethernet gives system integrators the ability to consolidate many jobs, or to alter the way they link equipment together. “Engineers have to think differently to gain the full benefit of the technology,” he continues.
The capabilities of the network also make it possible to link modules located at fairly long distances. Beckhoff is touting an approach that eliminates the delays of very long cable runs. It’s no longer necessary to be close to get real-time performance. “We can synchronize I/O down to the nanosecond level, providing deterministic I/O regardless of wire length,” Hansen says.
If membership in technical groups is any measure, interest in real-time Ethernet is high throughout the industry. Fieldbus Foundation has more than 300 members and the EtherCat Technology Group has more than 200.
All this attention to high-speed Ethernet moves the fieldbus wars to another level, looking at applications and protocols rather than all-encompassing proprietary architectures. But the competitive markets of this era make it likely that this fieldbus war won’t last nearly as long as the battles that began in the ‘90s. Most vendors don’t have the wherewithal to provide equal levels of technical aid for multiple solutions to one problem.“We can’t provide the same level of support for each bus, so we’re spending a lot of time evaluating which one will be our select bus,” says Brian MacCleery, group manager for NI’s Industrial Control and Measurement Group.
ARC’s Forbes notes that these varied solutions are “a point of confusion,” but that the diversity isn’t likely to have a major impact on market growth. The various guises of real-time Ethernet are linked to vendors, so many users will likely follow the lead of their key vendors.
However, the incompatibilities will show up when different vendors’ equipment must communicate. While this will be an annoying issue for many plant managers, it will be even more vexing for the system integrators who help them get plants functioning efficiently. For these companies, and forequipment suppliers who must work in heterogeneous applications, it often won’t be possible to pick only one.
The vendors promoting these disparate architectures want to provide differentiation, so they have little incentive to work toward finding a single solution. But most observers feel the field will narrow over time. “Eventually, this will resolve down to one or two leading architectures. The networks won’t all grow at the same rate, so the market will decide how many and which ones survive,” Forbes predicts.
Though there is significant momentum behind the expansion of Ethernet usage, observers note that the Institute of Electrical and Electronics Engineers (IEEE) standard isn’t the ultimate solution for current problems. In many applications, there’s still some need for a hierarchy of networks.
“There’s still cost associated with Ethernet switches for each device that needs a switch,” says Jim Remski, automotive powertrain business manager for Siemens Energy & Automation’s Automotive Business Unit, in Alpharetta, Ga. He points out that existing fieldbus switches are often embedded into equipment.
Remski also notes that lower-level buses that handle small amounts of data from sensors and other devices with minimal intelligence are sometimes the best solution. That sentiment is echoed by others.
“We don’t condone using Ethernet for everything. CAN (Controller Area Network) is good for products with small pieces of data like sensors,” says Hougland, of Opto 22. ARC’s Forbes notes that simple products such as proximity switches that don’t have diagnostics are another application where Ethernet may be too costly.
Another potential reason for avoiding Ethernet is its openness to viruses and hacker attacks. But for the most part, that’s a higher-level issue that doesn’t go down to the fieldbus level. That’s because it is not generally desirable to have equipment on a fieldbus communicating freely with any other device on the network. “You can configure the I/O so it only listens to communications from defined addresses,” Hougland says.
Though there are solid reasons for not using Ethernet everywhere today, that may not remain the case. Some observers feel that the semiconductor industry’s continuing drive to integrate more peripherals onto chips that cost less may eventually make Ethernet suitable in those low-performance applications. “When you can buy a microcontroller that has everything for under $5, Ethernet becomes basically free,” says NI’s Walters.
The low cost of microcontrollers is already making it easy for design engineers to include Ethernet on a growing number of products that tie into fieldbuses. As with many electronic technologies, once a couple of high end products incorporate a feature or function, it rapidly becomes a common attribute on many of the emerging new products.
“Many motor controllers have Ethernet now; they didn’t a couple years ago,” Hougland says.
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