Imagine having a car custom built to your specifications in just three days. Not an "option package" car, with various options lumped together, but a truly custom car, with individual choices of everything from paint color to upholstery material to tires to stereo system. You order your car on Tuesday, and you're driving it that weekend.
Farfetched? Yes, for now at least. But at least one of the many barriers to the three-day car—a lack of shared data between assembly lines and car makers' managers, dealers, and suppliers—could soon be disappearing. Ethernet is coming to factory floors, and it's connecting production equipment to the corporate and commercial worlds.
Ethernet in the factory means that shop floors can share data with corporate Ethernet networks and the Internet, providing advantages both in commercial collaboration and production. Plant-floor equipment, for example, can automatically submit real-time inventory requests that reflect up-to-the-minute—not forecast—materials requirements. These requests can automatically and directly go by e-mail to a manufacturer's inventory suppliers, eliminating human delay and paperwork. Ethernet can also bring large amounts of detailed plant-floor data into a company's front office, where decision-support systems can mine the data for trends that can lead to operational improvements.
So far, such data sharing has been limited, because Ethernet hasn't been totally suited to replace, or even to connect to, industrial fieldbuses. As a fieldbus, for example, Ethernet has lacked the real-time performance needed for fast, precise control of sophisticated production equipment. In addition, standard Ethernet doesn't have sufficient electrical noise immunity to operate reliably around high-energy devices such as welders. Office-grade Ethernet also has difficulty tolerating the high temperatures, mechanical stresses, and dirty conditions of industrial environments.
The outlook for plant-floor Ethernet is rapidly improving, though, as technology improvements bring higher speed, more ruggedness, and greater noise immunity. In addition, new configurations of Ethernet make it more deterministic than before, meaning that it's possible to more accurately predict the transmission-to-receipt time of an Ethernet message. Determinism—important for precise machine control—has until recently been the exclusive domain of certain fieldbuses.
Ethernet's suitability for harsh environments is improving in several ways. In areas of high electrical noise, for example, fiber-optic cable, instead of Ethernet's usual twisted-pair copper-wire cable, makes noise immunity essentially a moot issue. Fiber-optic cable is expensive, but prices are coming down, and, according to Robert McKeel, vice president of marketing for GE Cisco Industrial Networks (Charlottesville, VA, www.gecisco.com), its use is increasing. "In places where noise immunity really matters," McKeel notes, "they're going to pay the extra money."
Cable connectors—literally one of industrial Ethernet's weakest links—are improving, too. Ethernet's standard RJ-45 connector, in the form of a modular phone plug, is barely rugged enough for an office environment, says Paul Wacker, technical marketing manager for network-component supplier Lantronix (Irvine, CA, www.lantronix.com). Fortunately, says Wacker, several companies are starting to make RJ-45 connectors with added features for strength and durability. The RJ-45 connector may be surrounded, for example, by a screw-on, hermetically sealed, DIN-type housing that incorporates strain relief.
Even with technological improvements, however, Ethernet won't be replacing many fieldbuses anytime soon. Buses such as DeviceNet and Profibus, already abundantly in place, are still more suitable than Ethernet for many applications. It wouldn't be cost effective to connect Ethernet to a simple sensor, for example, and office-grade Ethernet can match fieldbus ruggedness only with costly additions and modifications, if at all.
Where Ethernet can't replace fieldbuses, it can link to them, connecting everything together and transferring data from intelligent devices to the front office.
To add an Ethernet link to existing equipment, you have several options. The easiest way is simply to add a small module that connects to an existing device's serial port on one side and to an Ethernet network on the other. A Lantronix Device Server, for example, is about the size of two decks of playing cards and includes all of the elements needed for device networking—a processor, a real-time operating system (RTOS), a TCP/IP network-protocol stack, and a web server.
If you want to design Ethernet into a product, rather than adding it on, many companies offer you both board-level and chip-level products to choose from. The Lantronix CoBox Micro Device Server, for example, is a small circuit board (1.6 × 2.0 inches) that implements all the functions of larger Lantronix modules. You can add it to your design simply by creating a circuit-board interface. For high-volume applications, you might consider a chip-level design, in which case you could employ an IC.
Ethernet still hasn't made big inroads in industrial environments, but its advantages are paving the way for it. One often-cited advantage is lower cost of components, because of Ethernet's high-volume production for commercial use. Another is simplified operations, because the same type of network can exist in offices and on the plant floor. Ethernet also offers easy connection to web-based software applications, enabling monitoring and control of plant-floor equipment from remote computers with a web-browser interface.
Probably Ethernet's biggest draw, though, is simply that it can move data back and forth between the plant floor and the wider corporate and commercial world. As GE Cisco's McKeel says, "People are now getting their arms around a lot of data, because they can, and it's going to give them a lot of benefits."
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