Simplify Your Network with Better Tools, Common Sense

Physically easier. Mentally tougher. That's the assessment of users, integrators, and suppliers, who say designing, building, and renovating industrial networks is becoming simpler and easier to optimize thanks to Ethernet's emergence, increased fieldbus compliance, and more suppliers developing improved hardware and software tools.

By Jim Montague Control Engineering January 1, 2001


Networks and communications


Device-level networks

Sensor/actuator-level networks

Local area networks

Sidebars: Ethernet coordinates, smoothes dragon float’s pneumatics Simple, appropriate network allows two-week oven installation Connecting process control and IT worlds—safely

Physically easier. Mentally tougher. That’s the assessment of users, integrators, and suppliers, who say designing, building, and renovating industrial networks is becoming simpler and easier to optimize thanks to Ethernet’s emergence, increased fieldbus compliance, and more suppliers developing improved hardware and software tools.

This means far less hardwiring, which reduces labor, maintenance, training, and other expensive, physical needs. It also helps plant-level networks reach up, connect, and deliver data to Ethernet-based administrative systems and vice versa. “The main change is that management wants to see what’s happening, and this is where we see the opportunity to use Ethernet to work with existing control networks,” says Paul Wacker, automation marketing manager, Lantronix (Irvine, Calif.).

The flipside, sources say, is that it’s psychologically harder to overcome the initial learning curve required to implement fieldbus protocols, Ethernet, and other sophisticated networking methods. Instead of traditionally dealing with one or two problems on many wires, some engineers’ headaches now involve handling many problems on one or two wires. These challenges include configuring routers, resolving data traffic issues, and solving other communication and software problems—even if they occur on one twisted-pair wire.

“Configuring a PLC is relatively easy compared to configuring a network router. There are a lot more variables, and it requires a totally different skill set,” says Bob Kirk, sales and marketing manager, Spyne Inc. (Pittsburgh, Pa.), a four-year-old network integration firm.

Fortunately, not only are new networking methods gaining momentum among users, many suppliers are developing and delivering improved networking devices and infrastructure equipment to satisfy users’ expected demands. These solutions and products can further simplify many networking projects, and help Ethernet and fieldbus achieve greater mainstream acceptance in manufacturing.

Climbing the learning curve

“Using rack I/O devices, plugging in cards, and working with PLCs may seem more straightforward, but users need to understand how flexible a fieldbus-based system can be,” says Charles Cook, advanced electronics products manager, Wago Corp. (Germantown, Wis.). “Also, while fieldbus may be easier for electricians, who don’t have to haul as much wiring, it may be an added burden for applications engineers, who have to configure it. That’s a price of achieving greater long-term flexibility.

“We support more than 10 fieldbus protocols, and so one of our biggest jobs is helping first-time users build these networks. Still, the learning curve is steep enough that initial fieldbus installations may not seem worthwhile, and sometimes savings aren’t achieved until the second project.”

Getting started

If you know what you want to do and what you have, then you also have a better idea of what you need and what you don’t need. This is a simple rule, but it remains the most powerful tool in designing, prioritizing, implementing, simplifying, optimizing, and maintaining industrial networks. Thoroughly understanding your business and manufacturing goals and capabilities can help you draft common sense specifications, resolve differences in networking methods, and secure the most efficient solution.

Besides simple awareness, several other guidelines can simplify networking projects. These include:

Compliance counts. The promise of open, interoperable networks is greater flexibility, simpler layouts, and increased component selection. However, communication obstacles remain, and users trying to solve specific manufacturing problems often simplify to one or two suppliers and their recommended networking methods that can handle most or all application requirements. Solving a networking problem today is generally more important than having flexibility that may or may not be needed in the future. Again, truly knowing your application and its needed capabilities can resolve trade-offs between openness and compliance.Beyond overall compliance, using single-source proprietary device- and control-level networks can be less expensive in some cases than many “open” networks because their chipsets are often more costly, according to Dave Quebbemann, industrial marketing manager, Omron (Schaumburg, Ill.). “Users just have to make sure that they’re comfortable being locked into one network or supplier.”One more benefit of compliance is that devotion to one fieldbus protocol or other network technology helps concentrate development and education related to it, according to Mike Bryant, director, Profibus and AS-Interface trade organizations (Scottsdale, Ariz.). “As fieldbus protocols mature, there are more adopters, which creates a software and tools market, and a wealth of lessons learned and instruction available,” says Mr. Bryant.

Some overkill OK. “Simpler is not always best. For instance, using Ethernet to replace an AS-i system (see sidebar) may be simpler, but it can cost more,” says Nick Jones, special projects manager, SST (Waterloo, Ontario, Canada). “To achieve true optimization, networking projects must take into account installation, training, and maintenance costs, as well as mean time between repair and mean time between failure calculations. In the short term, for example, an Ethernet network may not be as easy to debug as a more traditional one.”Mr. Jones adds that relatively smaller manufacturers may not have as precise performance targets as larger organizations, but that it doesn’t matter as much if a smaller user installs more capabilities than needed. “It’s human nature to play it safe, but it’s not useful to design a network based on emotion or fear,” he says.

Inherent compatibility. Much like settling on one supplier, users can also simplify their network projects by using bridging and gateway devices equipped with inherently compatible fieldbus protocols, which usually means they require little or no added configuration. For example, DeviceNet, ControlNet, and EtherNet/IP share this compatibility; Profibus PA, DP, and ProfiNet are designed to work together; and FOUNDATION fieldbus’ H1 and High-Speed Ethernet protocols can function cooperatively. Users must then ask, “How much configuration, software rework, or added hardware is needed to allow different parts of my network to communicate with each other at the speed, volume, and quality that they require?”Inherent fieldbus compatibility can also reportedly help device- and control-level networks reach up—usually via Ethernet—to enterprise and administrative systems. However, links between plant-floor and administrative networks usually require an added gateway, firewall, or quarantine device, so upper-level network traffic doesn’t disrupt lower-level functions. “Ethernet appears to simplify networks, but it also moves a lot of responsibility up to the management information system (MIS) level,” says Mr. Jones.

Ethernet, Ethernet, Ethernet

Though it clearly has the greatest potential to aid network simplification and optimization, far more people talk about Ethernet than have actually implemented it in plant-level applications—so far. Critics usually report that Ethernet lacks determinism, reliability, robustness, and redundancy. However, Ethernet appears to be steadily proving itself industrial settings. For example, the increasing speed of many Ethernet-based applications is already diluting claims of its non-determinism, says Eric Byres, research team leader, Advanced Information Technologies Group, British Columbia Institute of Technology (BCIT, Vancouver, B.C., Canada). “The criticism that Ethernet isn’t deterministic is a giant red herring,” he says. “Using Ethernet isn’t as hard as it’s made out to be.”

Spyne’s Bob Kirk adds that, “Ethernet can simplify your plant-floor board room connections, but you must first get onto that Internet protocol (IP) infrastructure. For instance, Fisher-Rosemount’s (Austin, Tex.) DeltaV system has controllers that use IP to talk to workstations, which means its data is already available via Ethernet. What you need next is a secure, reliable connection between the IT and process control networks. Firewalls, network routers, and intrusion detectors can provide reliable, secure, and safe Ethernet connections that prevent these potential problems (see sidebar).” Redundant processors and connectors, as well as enhanced power security, can also improve Ethernet reliability.

“The main lesson is: Don’t be afraid of Ethernet. You can do it. Just get the right information and people to help you implement it,” says Mr. Kirk.

Recent improvements

Besides linking to Ethernet and increasing cooperation within fieldbus protocols, several organizations are trying to meet users’ demands by improving communication between traditionally disparate protocols.

“Because some applications may need to services several protocols, we added multiple function blocks to FOUNDATION fieldbus’ HSE that allow it to interface with other protocols, such as ControlNet, DeviceNet, and Modbus” from Schneider Electric Automation (North Andover, Mass.), says Stephen Mitschke, applications engineer, Fieldbus Foundation (Austin, Tex.). Function blocks are pieces of software that allow devices on a network to identify themselves and their function, which gives users a picture or model of the network that can help manage traffic on it. Consequently, the mental challenges of industrial networking may soon become easier too.

Ethernet coordinates, smoothes dragon float’s pneumatics

Many control systems move, some are on the move, but only one animated a 60-ft dragon float in Detroit’s nationally televised America’s Thanksgiving Parade. Flicker the Dragon was built by The Parade Co. with help from Numatics Inc. (Highland, Mich.) and Creative Software Inc. (Ypsilanti, Mich.)

To smoothly coordinate pneumatic manifolds from Numatics that actuated Flicker’s moving tail, wings, head, eyes, ears, and other special effects, Creative Software used the Snap-B-3000-ENet Ethernet I/O relay controller from Opto 22 (Temecula, Calif.). Dan Katanski, Creative’s owner, wrote Visual C++ software on a laptop PC, which choreographed and ran the dragon’s moves, music, and sound effects. Sending real-time commands directly to the float’s on-board relay controller using 100 Base-T Ethernet over a point-to-point network connection using Microsoft Windows 98 communications software for TCP/IP Ethernet networking greatly simplified the software by eliminating communications protocol coding.

“Using 100-Mbps Ethernet gave us instantaneous control of all Flicker’s movements. If not for Ethernet, we would have used a much slower RS-232 connections, which would have worked, but wouldn’t have been nearly as effective,” says Mr. Katanski. “The IP protocol on Ethernet simplified software development, increased system reliability, and provides expendability for enhancing Flicker for next year’s parade.”

Simple, appropriate network allows two-week oven installation

Sometimes you don’t need all the networking bells and whistles. Tara Materials (Lawrenceville, Ga.) had only two weeks recently to install a new drying oven in its coated artists’ canvas line. The oven had an Allen-Bradley SLC 5/04 controller from Rockwell Automation (Milwaukee, Wis.) that had to be integrated with the rest of the 25-year-old line’s hardwired, relay logic-based controls.

Jim Pluth, Tera’s maintenance manager, just needed a simple PLC connection that was topologically flexible and easily expandable because the line’s existing I/O count and sensor locations were unknown. Faced with configuration, reliability, training, and topology obstacles posed by more sophisticated networks, Mr. Pluth selected an Actuator Sensor Interface (AS-i) system able to connect a total 248 I/O on a two-conductor cable at 5 msec in any topology. He also used I/O modules, masters, power supplies and accessories from Pepprl+Fuchs (Twinsburg, O.).

“A direct SLC 500 AS-i master was available for my PLC, and it didn’t require any added configuration software. I simply addressed the modules and connected them to the cable. Functions and setup were done with the SLC 500 ladder editor,” says Mr. Pluth, who adds that programming with AS-i was simple because its master is transparent and I/O data is mapped directly to memory.

Wiring for AS-i was slightly more expensive than conventional wiring, but Mr. Pluth reports Tara saved 75% on labor during installation by cutting design and wire pulling time from two weeks to two days for each task.

Connecting process control and IT worlds—safely

Using fieldbus, Ethernet, or even Internet-based methods to link administrative and plant-level networks is possible to varying degrees. However, despite the benefits, many users are reluctant because enterprise systems might interfere with costly manufacturing processes. To link these two realms safely and without slowing them down, Bob Kirk, of Spyne Inc. (Pittsburgh, Pa.), says there are at least four basic requirements:

Gateways —any one of several boxed devices that regulates traffic between IT/administrative and process control/plant levels;

Network routers —usually Internet-based hardware, which communicates at the network level of the Open Systems Interconnection (OSI) stack, and is configurable for specific users and functions;

Firewalls —software or hardware, usually embedded or distributed behind a router, which limits network access to predefined users; and

Intrusion detection —hardware and software that monitors networks for unauthorized users or events, and notifies the system administrator when any are found.