Plenty of automation pain has been caused by the lack of robust, reliable communications links between the PC-based world of IT network infrastructure and the sensors, actuators, and other process controls that manage the real-time factory-floor requirements of operational technology (OT). Industrial Ethernet systems require a high degree of determinism and reliability. In many factory automation applications, Ethernet has replaced legacy serial field bus connections because of its higher bandwidth and ability to link with enterprise networks. But Ethernet does not inherently have the deterministic response of field bus systems.
|The Deterministic Ethernet switching technology was developed to overcome the issue of competing Ethernet protocols. (Image source: Analog Devices)|
To overcome this limitation, the major industrial OEMs each defined their own Ethernet protocols, which have since become widely deployed open standards: PROFINET, EtherNet/IP, EtherCAT, ModbusTCP, and several others. Some of these protocols are fully compatible with standard TCP/IP Ethernet networks. Others have modified the data link, network, and/or transport layers (layers 2-4 in the OSI model) to achieve deterministic performance. Although these protocols can coexist with standard Ethernet, they are not interoperable with each other in a deterministic way.
The challenge when designing a network to support industrial Ethernet is to select a reference design that is compatible with a variety of different standards. The introduction of Industrial (or Deterministic) Ethernet partially addresses this problem, but the protocol incompatibility remains an issue. The protocols are simply not designed to interoperate, and they are prone to breaking down. This is especially problematic for companies that buy manufacturing equipment from multiple vendors.
Deterministic Ethernet Switching Technology
As the industry searches for an answer under the emerging set of IEEE standards known as time-sensitive networking (TSN), Analog Devices has developed a Deterministic Ethernet switching technology that is designed to break this bottleneck by allowing disparate, legacy Ethernet protocols to interoperate. “Ethernet for industrial networks has its challenges. They include latency, time synchronization, and the different protocols for different pieces of equipment,” Brendan O'Dowd, general manager for industrial automation at Analog Devices, told Design News. “If you’re an automation supplier, you need to talk to different protocols. On the path to unification, we’re moving toward TSN, and there are standards around that.”
O’Dowd noted that the switching technology provides manufacturers with a path toward TSN readiness without the need for expensive equipment upgrades. “It makes it easier for companies to choose the equipment that best suits their manufacturing needs, regardless of vendor,” said O’Dowd. “This meets the challenge of going from the Ethernet standards around the factory to the reality of sending more data and sending data faster. If you have robots, the level of precision you need is in the hundredths of nanoseconds. The protocols we have now don’t scale to that easily.”
Rob Spiegel has covered automation and control for 17 years, 15 of them for Design News. Other topics he has covered include supply chain technology, alternative energy, and cyber security. For 10 years, he was owner and publisher of the food magazine Chile Pepper.
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