PCs, Ethernet occupy factory floor

PCs, Ethernet occupy factory floor
The factory floor's long-awaited move toward PC controls and Ethernet-based communications isn't complete, but industry analysts say they expect major progress in 2002. "Some of the biggest manufacturers will be moving more and more toward PCs," noted Dick Slansky, senior analyst for ARC Advisory Group (Dedham, Mass.). "They want to leverage the existing hardware infrastructure on the factory floor, instead of buying new programmable-logic controllers.

"Companies want to start connecting their supply chain management systems to their customer relations," Slansky said. "They want to track their machinery and their assets more closely. And they can't do all of that with programmable-logic controllers [PLCs]. They're going to have to bite the bullet and move into PC control."

The PLC, invented in 1970 as replacement for electrical relays, has continued to serve as a control device on the factory floor because engineers trust it. "People have been sounding the death knell for the PLC for a lot of years," Slansky said. "But it's obvious that it's not going to go away in certain applications."

Most of those applications involve smaller numbers of I/O and limited connectivity to the front office. But the higher-end applications are increasingly moving toward PC control.

Until recently, many engineers have been wary of using PCs because the platforms lacked determinism. But a recent survey by Industrial Controls Consulting (Fond du Lac, Wis.) revealed that fears about the PC's determinism have dropped dramatically over the past decade. According to the survey, whereas 10 years ago 90 percent of factory automation engineers were concerned with PC reliability, only 20 percent are concerned today. "If you ask engineers whether they expect to use a PC on the factory floor five years from now, 85 percent say yes," said Tom Bullock, president of Industrial Controls Consulting.

As manufacturers look more seriously at PC control, experts say that Ethernet-based communications are also inevitable.

For most manufacturers, they say, the move to Ethernet data bus communications will occur in three distinct steps. First, manufacturers will tie the front office to the plant floor via Ethernet. Next, they will do peer-to-peer connections (PLC to PLC or PC to PC) via Ethernet. Finally, they will bind controllers to lower-level devices — such as motors, drives, actuators, optical sensors and proximity switches — over Ethernet.

The final step is believed to be several years away for most manufacturers, especially those that have invested heavily in specialized industrial data buses, such as DeviceNet and Profibus.

Omron's Wireless DeviceNet will bring wireless communications to the factory floor in 2002.

Major industrial vendors are already offering Ethernet solutions. In 2000, GE Industrial Systems and Cisco Systems Inc. formed an alliance for bringing Ethernet to the factory floor. The venture, known as GE Cisco Industrial Networks (Charlottesville, Va.), installs network hardware, including cables, switches, routers, hubs and firewalls, for manufacturers wanting to migrate toward Ethernet communications.

Similarly, Rockwell Automation (Mayfield Heights, Ohio) has introduced a suite of products designed for use on a 100-Mbit/second Ethernet application layer.

Such introductions have generally been aimed more at costlier products, such as host controllers and operator panels, than at less-expensive items, such as motors and sensors.

Many industrial vendors sense that engineers are eager for such product introductions. A recent study by Industrial Controls Consulting revealed that U.S.-based system integrators chose Ethernet by 3 to 1 over DeviceNet and 9 to 1 over Profibus.

Ultimately, the commodity nature of PCs may make Ethernet an irresistible choice for the industrial community, analysts say. Because Ethernet products can leverage the development work done previously in the desktop world, they will eventually offer lower costs than today's device networks.

"The driving force will be cost," Bullock said. "Ethernet may be more sophisticated than the factory floor needs right now, but it's going to be cheaper than today's device networks, so it will gain popularity."

Wireless future
Even as many engineers prepare for a factory floor future with Ethernet, a handful of forward thinkers are casting their gaze a few years beyond that. Some foresee a day when sensor-packed machines will talk to host controllers across hundreds of feet, without a network cable. "Wireless will begin to invade the factory floor over the next 10 years in a big way," said Bullock. "It's in its infancy right now in factory automation, but once the right technology is developed, applications with long runs, such as transfer lines, will need it."

Thus far, however, engineers have been unable to agree on the appropriate wireless technology for the factory floor. At a recent Intel Developer Forum, Rappore Technologies Inc. showed a Bluetooth solution that took control input commands from a Bluetooth-equipped notebook computer and remotely operated a robotic arm complete with pincer, wrist, elbow and shoulder.

Many controls engineers are leery of using Bluetooth protocols for large manufacturing applications, saying that Bluetooth lacks sufficient broadcasting range and costs too much.

Omron Electronics LLC (Schaumburg, Ill.) offers an alternative in its Wireless DeviceNet, designed for radio transmission of input and output signals in a factory environment. The product, based on industrial DeviceNet protocols, uses spread-spectrum technology and operates at 2.4 GHz. The company foresees the technology's being used to enable controllers to communicate with wireless pressure sensors, temperature sensors and flow meters in the factory.

"In many cases, it will make more sense to do it wireless, as opposed to running wires out to every sensor," said Bill Arnold, product-marketing manager for networks and communications products at Omron. n

Omron's Wireless DeviceNet will bring wireless communications to the factory floor in 2002.