What is EtherCAT® used for?

In the complex ecosystem of industrial automation, connecting disparate devices – drives, sensors, I/O modules and safety controllers – is a fundamental requirement. As engineers design systems for precision motion control, the choice of communication protocol dictates the architecture of the entire machine. Among the various industrial Ethernet standards, EtherCAT is widely used to synchronize process and motion equipment for general industrial automation applications.

EtherCAT is a common choice for motion controller programming when linking a central controller to various nodes on a network. Its adoption is driven by its ability to offer deterministic performance over standard cabling, making it a functional solution for factory-wide connectivity. However, while it serves as a backbone for general automation, understanding its limitations helps engineers decide when to employ it for connectivity versus when to leverage higher-performance proprietary buses for critical motion tasks.

What is the purpose of EtherCAT?

The primary purpose of EtherCAT (Ethernet for Control Automation Technology) is to serve as a real-time industrial communication protocol. Invented in 2003, it was designed to overcome the non-deterministic nature of standard Ethernet in automation environments.

EtherCAT explained simply is a method for processing data "on the fly." Rather than treating data packets like standard network traffic that must be received, interpreted and forwarded at each stop, EtherCAT allows a single frame to traverse the network. As the frame passes through each node (or SubDevice), the device reads the data addressed to it and inserts its own feedback data into the stream without stopping the frame.

This architecture is used for:

• Connecting Large Networks: The protocol supports up to 65,535 nodes on a single network, making it scalable for factory automation.

• General Device Synchronization: It aligns the timing of servo drives with I/O devices for general coordination.

• Cost-Effective Control: By using standard Ethernet cabling, it provides real-time capabilities without the need for specialized interface cards on every device.

How is EtherCAT different from Ethernet?

While EtherCAT is based on Ethernet hardware, its operation differs from the standard Ethernet (TCP/IP) used in office environments. The distinction lies in data handling and transmission predictability.

Standard Ethernet is not deterministic. Data packets are subject to collisions and routing delays, introducing latency and jitter that varies with network traffic. This variability is generally unacceptable for closing servo loops in motion control applications.

In the EtherCAT vs Ethernet comparison, EtherCAT uses a MainDevice and SubDevice architecture to control network timing. Using distributed clocks, EtherCAT aligns the time base of SubDevices, typically achieving a jitter of less than 1 microsecond. While this improves upon standard Ethernet, 1 microsecond of jitter can introduce errors in high-precision applications. In contrast, proprietary optical buses like HyperWire^® reduce jitter below the nanosecond level, providing the tighter synchronization required for complex, multi-axis precision motion.

Does EtherCAT use an Ethernet cable?

Yes, EtherCAT uses standard Ethernet physical layers and cabling, specifically CAT5 or higher copper cables. This contributes to its adoption by using inexpensive, readily available infrastructure.

However, the use of standard EtherCAT cable hardware introduces limitations regarding signal integrity. Copper cables are sensitive to electromagnetic interference (EMI) and electrical noise . In electrically noisy factory environments, this sensitivity can compromise signal integrity and lead to communication faults. Furthermore, standard EtherCAT is limited to 100 Mbps bandwidth.

What PLCs support EtherCAT?

Because EtherCAT is an open technology managed by the EtherCAT Technology Group (ETG), it is supported by various manufacturers. This openness allows engineers to integrate components from different vendors into a single system.

Many major PLC and controller manufacturers support EtherCAT, enabling a MainDevice to control a vast array of SubDevices. However, relying solely on a PLC over EtherCAT for complex motion can limit performance due to the bus's cycle rate and jitter constraints.

For precision motion, a hybrid architecture is often preferred. A specialized motion controller, like the Aerotech Automation1 iSMC, can operate as a "Controller SubDevice." In this setup, the controller manages complex motion paths locally on a high-speed HyperWire fiber-optic bus while communicating process data to a central third-party PLC over EtherCAT. This approach uses EtherCAT for general connectivity while relying on the superior performance of HyperWire for the critical motion mechanics.

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