EtherCAT®: Ethernet for Control Automation Technology and its Advantages for Precision Motion Systems

The fastest Industrial Ethernet-based fieldbus system keeps gaining popularity for a variety of reasons.

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EtherCAT® is a modern, cost efficient, open real-time Ethernet-based fieldbus system. It is a registered trademark and patented technology, licensed by Beckhoff Automation GmbH, Germany. EtherCAT is short for “Ethernet for Control Automation Technology” and is used by control and system engineers as a robust, high-speed, real-time network for machine control solutions. The flexibility of the fieldbus system and the precise synchronization of all network devices help EtherCAT to gain popularity on a global base.

Real-time networks are characterized by

  • High degree of reliability
  • Very precise timing
  • Deterministic behavior with guaranteed response times

Precision automation applications and cutting edge machine control solutions require fast data update rates, or cycle times ≤100µsec along with very low latency and low communication jitter. When multiple axes and events need to be synchronized exactly, jitter as little as 1µsec can already have a negative effect on the system performance.

Why use EtherCAT?

High-speed gantry system for inspection, based on ACS EtherCat control technology (Image: PI)
High-speed gantry system for inspection, based on ACS EtherCat control technology (Image: PI)

Performance

EtherCAT is the fastest industrial Ethernet technology and can synchronize with nanosecond, accuracy significantly improving application efficiency.

Flexible Topology

EtherCAT doesn’t need hubs or switches that limit conventional Industrial Ethernet systems, making it virtually limitless when it comes to network topology. Line, tree, star topologies and any combinations thereof are possible with a nearly unlimited number of nodes. The network topology is only determined by the machine structure.

Simplicity and Robustness

Since EtherCAT doesn’t require switches and active infrastructure components, the costs for these components and their installation, configuration, and maintenance are also eliminated. The Ethernet fieldbus makes configuration, diagnostics, and maintenance easier, reducing system costs.

Hexapod 6-Axis motion platforms provide flexibility and unique features such as a user programmable pivot point. The EtherCAT interface guarantees an easy connection to parent PLC or CNC controls to simplify integration and synchronization of hexapods other motion and automation components. 6D Positions are simply commanded in Cartesian coordinates. The PI EtherCAT hexapod controller handles all required transformations for tool or work coordinate systems. (Image: PI)
Hexapod 6-Axis motion platforms provide flexibility and unique features such as a user programmable pivot point. The EtherCAT interface guarantees an easy connection to parent PLC or CNC controls to simplify integration and synchronization of hexapods other motion and automation components. 6D Positions are simply commanded in Cartesian coordinates. The PI EtherCAT hexapod controller handles all required transformations for tool or work coordinate systems. (Image: PI)

Affordability

EtherCAT delivers the features of Industrial Ethernet at the price of a classic fieldbus system because no expensive interface cards or co-processors are necessary. The master device simply requires an Ethernet port.

Precision Automation Sub-Systems

PI precision automation sub-systems are based on ACS motion control hardware, benefiting from EtherCAT integration.

EtherCat-based modular motion controllers provide the brain power to run multi-axis systems with advanced functions such as InputShaping and gantry control to focus on maximum throughput in industrial nanopositioning applications. (Image: PI / ACS)
EtherCat-based modular motion controllers provide the brain power to run multi-axis systems with advanced functions such as InputShaping and gantry control to focus on maximum throughput in industrial nanopositioning applications. (Image: PI / ACS)

EtherCAT Technology Background

An EtherCAT network includes one EtherCAT Master and one or more EtherCAT nodes. One network can include a maximum of 65,535 nodes.

Example of EtherCAT configuration using a star topology
Example of EtherCAT configuration using a star topology

Since EtherCAT was introduced in April 2003, more than 4500 companies around the world have developed EtherCAT-based products and related software – which is easily explained given its exceptional performance, flexible topology, simple integration, and robustness.

What Network Topology Is Supported by ACS Hardware?

Line, ring, and star topologies are supported. Ring topology NetworkBoost™ is a feature that increases system uptime and productivity by network failure detection and recovery. The star topology, based on EtherCAT junctions, might be beneficial when using the Flexible Configuration feature which enables disconnecting groups of nodes during machine operation.

Synchronization: What Cycle Times Can Be Achieved?

In high performance applications exact synchronization is a critical factor. ACS nodes are synchronized applying the EtherCAT Distributed Clocks (DC) mechanism. The controller supports short cycle times: 1msec, 0.5msec, 0.25msec and 0.2msec (1, 2, 4 and 5 kHz).

Perfect synchronization between galvo scanners and linear motion systems allows stitching-free wide-field laser scanning systems with virtually infinite field of view.
Perfect synchronization between galvo scanners and linear motion systems allows stitching-free wide-field laser scanning systems with virtually infinite field of view.

Integration of Third Party Products Made Simple

Non-ACS DS402 Drives and other types of EtherCAT nodes are commonly used with ACS controllers. The integration with other ACS products in the same EtherCAT network is easy and does not require any special adjustments.

Motion Subsystems Controlled by Third-Party EtherCAT Master

The new SPiiPlusES can also be controlled by a third-party EtherCAT Master. SPiiPlusES is a motion controller for ACS “internal” networks and, as an EtherCAT drive, supports up to 8 axes according to DS402 standard. In addition, it can be used as EtherCAT bridge, providing the functionality of synchronized data exchange between the non-ACS and ACS networks.

Advanced control algorithms, such as ServoBoost (optimize step-and-settle times), and NanoPWM (tracking with subnanometer precision) are then available within the existing network.

ACS Motion subsystem in a third party EtherCAT network
ACS Motion subsystem in a third party EtherCAT network

PI and ACS provide motion centric solutions for industrial automation such as those in assembly, semiconductor manufacturing, mechanical engineering, laser material processing, inspection systems, and in additive manufacturing.

An integrated Ethercat® based controller (4 to 8 axis) integrating closed-loop digital servo control, drivers, and power supply in a 19”rack mount design, delivers up to 2000W power.
An integrated Ethercat® based controller (4 to 8 axis) integrating closed-loop digital servo control, drivers, and power supply in a 19”rack mount design, delivers up to 2000W power.

About the Author
Boris Brevdo is a Senior Software Engineer at ACS Motion Control

 

Further reading

Learn more about PI Precision Motion Systems, Stages, Components: www.pi-usa.us/products/index.php

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About PI

PI (Physik Instrumente) is a leading manufacturer of precision motion control equipment, piezo motors, air bearing stages and hexapod parallel-kinematics for semiconductor applications, photonics, bio-nano-technology and medical engineering. PI has been developing and manufacturing standard & custom precision products with piezoceramic and electromagnetic drives for 4 decades. The company has been ISO 9001 certified since 1994 and provides innovative, high-quality solutions for OEM and research. PI is present worldwide with fifteen subsidiaries, R&D / engineering on 3 continents and total staff of more than 1,000.

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