Ethernet is a fact of life. Once the province of Information Technology (IT) departments, it now reaches down to the controls and, increasingly, to the input/output (I/O) level. The advantages of enterprise-wide Ethernet networks, according to Dan Knight, an industry solution manager for Ethernet to the Factory for network equipment vendor Cisco Systems Inc., San Jose, Calif., are many.
“Manufacturers are competing in a global environment, often against companies with lower cost structures,” notes Knight. “As a result, manufacturing companies need to be more flexible and efficient to be successful in a globally competitive market. By integrating data from different functions throughout the value chain, from the factory floor to supply chain through to engineering and sales and service, Ethernet enables that flexibility and efficiency.”
However, this new world of Ethernet-based automation brings challenges as well as opportunities. Along with obvious security issues, it creates a situation in which network management can no longer be strictly an IT affair. Control engineers must now take on some of the burdens of network management, interfacing more closely with IT in the process. It’s not always a comfortable situation.
“This is a challenge for many companies right now as the automation networks and traditional IT networks are starting to converge,” Knight notes. “It’s an issue that has people and technology components.” On the technology side, Cisco stresses the importance of what it calls usability tools in its “Ethernet to the Factory” suite of products—tools that can reduce the level of network expertise a control engineer needs to deploy and maintain automation networks.
One of the key usability tools deployed by Cisco and others is the intelligent switch. These are managed switches with embedded software that helps optimize Ethernet networks. For one thing, they allow users to set up virtual local area networks (VLANs) to link devices in logical groups, even if those devices are in disparate locations. Thus, machine controllers in different buildings can be interfaced from a single location.
Importantly, these switches help ensure device availability through traffic management features. For instance, some I/O devices have limited reception capability, so switches can manage multicast traffic, directing that traffic only to desired recipients so that devices aren’t overwhelmed with unwanted and unneeded messages. Intelligent switches can also prioritize traffic so that mission-critical data, such as motion control information, receives highest priority and always passes through the network even if the network is congested. Knight stresses that these switches’ auto-configuration options, together with the fact that configurations can be stored on flash memory devices for quick replacement, helps simplify control level network management so that “control engineers don’t need to become network/IT experts.”
Best of all, using network management software, intelligent switches can be deployed relatively easily with the aid of a simple, graphical interface and a standard personal computer (PC) browser.
Beyond the switch, several types of dedicated traffic management systems exist. Among these are WebMux traffic management and load balancer systems from Avanu, of San Jose, Calif., units that boast easy configuration, and PC-based protocol analyzers from Frontline Test Equipment, of Charlottesville, Va. Frontline’s systems monitor networks in an effort to identify communication problems quickly, before they become major headaches.
Seeing is believing
If you want your control engineers and other plant floor professionals to take a greater role in managing the network, why not start by letting them look at it. That’s the rationale behind IntraVue software from Network Vision Inc., Newburyport, Mass.
IntraVue is a network visualization tool designed to give control engineers the ability to identify problems on the network by automatically mapping all Internet protocol (IP) devices in a network and showing their communication status on a single graphical display. In some cases, this helps control engineers aid the IT department in correcting a problem quickly. In many cases, though, it enables the plant floor personnel to correct the problem themselves. That’s because, according to Network Vision President Mark Fondl, most network disruptions are caused by the failure of the connected devices operating in the harsh plant floor environment, not by software.
“I saw that the control technicians didn’t have useful tools,” recalls Fondl. “The IT tools were geared toward network infrastructure and not toward what would happen if you placed connected devices in a hostile environment with its power surges and its extremes of temperature, vibration and noise. It was similar to the very early days of PLCs (programmable logic controllers). Back then, technicians had nothing to view, they couldn’t look into the logic of the PLCs. Then, relay ladder logic came along and allowed them a graphical view. We said, ‘Let’s take the same approach—a very visual, very graphic approach—to identify the precise location of a fault and provide the technician with the info to repair that fault.’ ”
Fondl notes that Network Vision’s essential business is in providing support to people who don’t know how their networks are constructed, and don’t know how many devices are where. “That’s the beauty of Ethernet—and the problem,” he says. “A lot of people are afraid of the net, but those same people have Internet skills. Why not empower them to use those skills? That’s what we’ve tried to do—if you can work a mouse you can work IntraVue.
Fondl adds that automation systems have traditionally taken complex issues and allowed people with few skills to operate them. “We said, ‘Let’s take this same approach to Ethernet.’ ”
And the cost of providing plant floor folks with this level of network management? “Now that Ethernet is being used for real-time communications, any disruption can shut down a facility,” Fondl observes. “So when people ask me what’s the cost of IntraVue, I tell them, ‘About one half hour.’ ”
Fondl notes that when it comes to questions of network management, the relationship between the plant floor and IT is not always a smooth one. “Today, there’s a big issue over control of the net—whose responsibility is it?” He says that IT departments often feel they own the network and are reluctant to share that ownership, yet the controls groups need to be able to assume more responsibility for their own bailiwick, the plant floor portion of the network. He feels that change is gradually taking place. “I think it’s an educational process.”
That’s an assessment that Jeremy Bryant, automation market network specialist for Siemens Energy & Automation Inc., the big Alpharetta, Ga.-based automation supplier, seems to agree with. “The biggest thing is for control systems personnel to understand is that they can utilize Ethernet to attach themselves to the office environment and still get all the benefits of automation. Its features are features that the automation world needs, and are configurable in ways they can relate to.” Among those features is the ability to access diagnostic information from switches, something that Bryant feels the control world is still not fully aware of.
“Earlier networks like Fieldbus weren’t designed for peer-to-peer communication,” continues Bryant, “most of them being master-slave, and there were limitations on data size and number of nodes. So there are good solid reasons why Ethernet is starting to dominate in the control world. However, if it’s Ethernet, there’s a belief that IT owns it.”
This sort of attitude inhibits the realization of Ethernet’s full potential, but it’s changing—gradually. “Now with Ethernet being used in more and more control systems, the automation and IT people have to come together. This is evolving plant- by-plant, with the more innovative plants leading the way.” Bryant cites the coordination of IP addresses as one key area of divergence, with IT employing Dynamic Host Configuration Protocol (DHCP) to assign addresses to devices that enter the network, while on the plant floor, this is often done manually. Vendors are seeking to address the problem with offerings such as Network Vision’s Auto-IP—software that works in conjunction with the IntraVue system to automatically assign the correct IP address to a new device upon power-up.
“The controls and IT worlds have to evolve a closer working relationship,” Bryant reiterates, citing training as one of the key ways of making that happen. Opto 22, a Temecula, Calif., automation vendor, has been plowing that furrow for several years with a week-long class, held twice a month, that covers basic Ethernet and networking topics, in addition to Opto 22 products.
“We found you can’t just tell folks that your IT or net control engineers will help if you have a problem,” says Alexi Gray, director of training for Opto 22. There must, she insists, be at least a basic level of net savvy on the plant floor.
“In our class, we show you how to configure and how to test. We find that control engineers are really getting into this. They may not be IT people, but they want to own their systems. We teach a variety of other subjects, including IP addressing/DHCP, and also spend time on switches. The control-level folks need to understand switches, how they operate, what they can do and how they can use them.”
Jeff Owens, a Dallas-based consultant specializing in industrial control system design and programming, went through the class. He was one of the folks who felt the need to know more about the network that was impacting his domain. He describes himself as increasingly involved with networking concerns.
“Over the years,” says Owens, “I’ve been from ‘Ethernet is not suitable for a control network,’ to ‘The Ethernet control network should be completely separate from the business network,’ to ‘Boy, it sure is great when we can share all this control data right over the network!’ I’d thought that Ethernet was fine for HMI (human-machine interface), but not for much else in the control environment because it’s non-deterministic. My thinking shifted when 100 Mbps (megabits per second) Ethernet became more available and switches became cheaper. Technically, Ethernet is still not deterministic, but throughput is so fast that it’s not really an issue.
“With two network cards in the PC, one to the controller or test stand, the other to the office network, you can tie that controller right into the office network. Along with passing data upward, we’re also tying in some of the office applications so we can take the data and interface it pretty easily into the controller. This is pretty new, but it makes sense to give the engineer direct access to some of this data.”
The emerging field of wireless networking is also promising to give engineers and other manufacturing professionals real-time access to an expanded range of data. As Hesh Kagan, director of new ventures at automation vendor Invensys Process Systems, Foxboro, Mass., notes, “The radio spectrum immersing every enterprise is a communications asset to be exploited. The good news is that the emergence of secure, affordable wireless technology is making it easier to do that every day.” Unlike traditional networks, however, where control-level personnel are taking greater control, wireless networks remain a top-down affair.
“Unlike wired networks, which are virtually as expandable as budget permits, each enterprise is endowed with only a finite amount of radio bandwidth, and this must be shared across multiple departments—departments that may have had little need to coordinate activity in the past,” Kagan explains. “Also, unlike wired networks, some access to which can be restricted physically, wireless frequencies are accessible with even the most rudimentary wireless communications devices. This finite, relatively available resource means that today—and for likely many years to come—reaping the many control benefits of wireless communications challenges technology management much more so than technology performance.”
Kagan adds that Invensys, in conjunction with its partner Apprion, of Moffett Field, Calif., is working to meet those challenges by developing a unified systems model that can accommodate multiple wireless technology vendors.
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