vision systems, I/O and other feedback devices. The engineers specified an XMP-SynqNet-PCI-based controller to coordinate the axes and custom dual-axis SynqNet servo drives from the Kollmorgen Servotronix Group of Danaher Motion, in Wood Dale, Ill.

Besides offering high-speed, synchronous servo update rates, the network also gives them the ability to have PC-based centralized control, execute client-enabled motion, download firmware configurations and perform remote diagnostics. It also lets the engineers use Danaher’s sophisticated programming, tuning and testing software. “I could excite any axis or two axes simultaneously and see the frequency response of the system,” says Mike Krolak, senior director of controls technology at Asyst.

Past Propriety Protocols

Developments have made Ethernet suitable for motion control—without the proprietary protocols that have been necessary in the past, according to Matheus Bulho, product manager for motion control at Milwaukee-based vendor Rockwell Automation Inc. This means that users should be able to simplify their network architectures with off-the-shelf technology, rather than deploying different networks for motion control, sensors and enterprise communications.

One of these enabling developments is the mechanism for prioritizing packages sent over the network. Another is switching technology that manages the traffic to allow sending and receiving data at the same time in a true duplex fashion. Older Ethernet duplex technology either sent or received data. The last of the developments is a synchronous clock defined by the IEEE 1588 standard promulgated by the Institute of Electrical and Electronics Engineers. “It allows us to synchronize nodes on the network within 200 nanoseconds,” reports Bulho.

Rockwell’s EtherNet/IP fieldbus made strategic sense for W&H Systems Inc., a Carlstadt, N.J.-based supplier of merchandise sorters and other handling equipment for retailers and distribution outlets. “When Rockwell announced its Ethernet-based medium for controlling I/O, we looked into replacing our Profibus technology with it,” says Kevin Kiefer, senior controls engineer at W&H Systems.

The handling-equipment builder had been growing and attracting larger customers that needed bigger conveyor-based systems with hundreds of lanes. “As our sorters became larger, it became more difficult to make our Profibus network fast enough to recognize changes in device states,” explains Kiefer.

The engineering staff tested the new fieldbus initially on a small version of the company’s Reliable Sorting Unit (RSU). The real test, however, came when a huge mail-order house needed an RSU-based sorter with more memory and features than any that W&H had built before. The builder would not have attempted the project with Profibus technology because the program size and physical network medium would have made the device update times too slow to track and sort merchandise correctly, according to Kiefer.

The sorter’s enclosed-track conveyor would have to circulate 615 tilted carrying trays among 330 diverting chutes. A scanner would read the bar codes of the products in the trays, so the appropriate diverter could direct them to holding bins for delivery. “The new automated system needed to be able to track materials throughout the process at rates up to 50 percent faster than the previous system,” says Kiefer. Yet, it had to fit in the same 6,400-square-foot space and provide the house’s maintenance crew easy access to the mechanical components.

The Ethernet-based fieldbus did the job, communicating 10 times faster than the old network. Not only can the new sorter handle 120 pieces per minute, but its simpler architecture also cut engineering and programming costs by 40 percent and installation time by 20 percent. “We came in early,” says Kiefer. It took only two weeks to put this network into motion.

For more information, search keywords “ motion control ” at www.automationworld.com.