Machine Design

Software Calms Machine Jitters

Electronic commands passed from machine to machine over data networks drive many modern production lines.

But timing irregularities in the signals from even one machine — a difference of only a tenth of a second — can result in havoc on the plant floor. These timing glitches, called “cyclic jitters,” can make machines jump or shake, damaging products, even shutting down entire assembly lines. Fortunately, software recently developed by engineers at the National Institute of Standards and Technology (NIST) should help calm those jitters.

NIST’s EtherNet/Industrial Protocol software tool helps manufacturers anticipate how machines will perform. And data from the tool can improve performance.

Different vendors define the performance of network devices in various ways. These differences make it difficult for manufacturers and plant engineers to compare high-speed data transmission of similar devices. To determine how performance characteristics relate requires time-consuming searches through vendor manuals or spending hours contacting vendors. Although standardized tests can indicate how well devices conform to communication specifications, until now manufacturers couldn’t be sure how well the devices worked under normal or heavy transmission conditions on the factory floor.

The software collects device information from the user, generates test scripts based on that information, analyses performance data, and reports results to the user. The software provides transmission data for three conditions: no background traffic, small background traffic, and over 240 devices on the network.

NIST began the project at the urging of U.S. Council for Automotive Research (USCAR) Plant Floor Controllers Task Force and developed the program with the Open DeviceNet Vendor Assoc. ODVA, a vendor organization that maintains the DeviceNet and EtherNet/ IP standards used extensively by the U.S. automotive industry, plans to begin using the test tool later this year.


The points on this graph from NIST’s EtherNet/IP software represent data packets. Points away from the centerline reflect timing errors in the network communications of the device.

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