Because Ethernet is collision-based and not inherently deterministic, many smart people across the globe have been hard at work improving both hardware and software to ensure that the industrial needs for real-time operations and continuous uptime are being met. The result is that industrial network availability techniques are improving.
As Terry Costlow reports, network fault tolerance is becoming more cost-effective, especially for small and midsize manufacturers. Physical enhancements, like dual Ethernet connections on controllers, are more easily enabling redundant networks.
Most major control system manufacturers now incorporate versions of Ethernet networks and higher-level Ethernet-related protocols in their product offerings. Automation World columnist Jim Pinto, who shares his views on how fieldbus networks compare to industrial Ethernet networks in his May 2013 column (bit.ly/awslant69), says that “more than 20 different protocols compete in various segments of this rapidly growing market, each offering adaptations to meet different real-time and cost challenges.” Here are some of the leaders he cites:
• Profinet is the open industrial Ethernet standard promoted by Profibus International (PI, us.profinet.com). This group claims that more than 2 million Profinet devices are currently installed in plant environments; more Profinet than Profibus engineers were certified in 2012.
• EtherCAT (Ethernet for Control Automation Technology) originally developed by Beckhoff (www.beckhoff.com), provides real-time performance and supports various topologies with twisted pair and fiber optic media.
• EtherNet/IP (IP for “industrial protocol”) is supported by Rockwell Automation-affiliated organizations (www.rockwellautomation.com), ControlNet International (CI) and Open DeviceNet Vendors Association (ODVA, www.ODVA.org).
• Modbus-TCP allows the widely used Modbus protocol to be carried over standard Ethernet networks on TCP/IP.
• Ethernet Powerlink, introduced by Austrian automation company B&R (www.br-automation.com), combines CANopen and offers deterministic real-time operation.
• CC-Link (www.cclinkamerica.org) IE Field is another variant, originally developed by Mitsubishi and now an open standard.
With so many working on Ethernet for industrial use, greater availability and better functionality is inevitable.
>> Renee R. Bassett, [email protected], is Deputy Editor of Automation World.