EtherCAT Plays a Role in Multiple Industries

“We use EtherCAT to facilitate fast, reliable control of our special effects systems in permanent installation and concert touring settings,” says Shep Dick, research and development engineer at Image Engineering. EtherCAT also allows him and his colleagues to configure their equipment remotely and to obtain real-time feedback.

The PC-based automation controllers that Image Engineering obtains from Beckhoff Automation have the intelligence to coordinate pyrotechnics and moving objects safely. The controls also enable complex user interfaces using Beckhoff’s TwinCAT human-machine interface (HMI) software.

“The flexible topologies and interoperability of EtherCAT-based technologies give us the adaptability and reliability we need to integrate our special-effects systems efficiently,” says Dick. “And Failsafe over EtherCAT [FSoE] allows us to incorporate the most important parts of our special-effects units, the safety systems, into the same cabling and software we use for network control.”

Wide applicability across industries

Though an entertainment company like Image Engineering is not a manufacturer, like readers of Automation World, their application of the technology underscores its wide applicability.

Robert Trask, PE, North American representative at the ETG, says, “EtherCAT is often used for motion control in many industries because of its short cycle times and high determinism. It also outshines most other industrial Ethernet networks in applications that need flexibility in topology and linking many nodes. That’s why EtherCAT enjoys wide adoption in a mix of applications across many industries.”

What is EtherCAT?

The primary difference between EtherCAT and other industrial Ethernet protocols is that EtherCAT does not use IP (internet protocol) addresses or switches. It operates on standard Ethernet at the physical level, but uses Ethernet in a way called “Ethernet-on-the-fly.” This name comes from the fact that individual nodes on the network need not receive the entire frame before processing it.

“An Ethernet frame using EtherCAT data travels through each node on the network the same way every cycle, and every node extracts and inserts its data on-the-fly,” explains Trask. “As the system initializes, the controller goes to each device and asks, ‘What are you reading and writing?’ Then, it determines the location of that node’s data within the frame. This is the logical process image and it is highly optimized and predictable.”

Because each device processes data as it passes through, processing it on the fly, dedicated switches and complex network configurations are unnecessary. This helps eliminates unnecessary communication delays as well as hardware costs.

As a device-level protocol, EtherCAT is not intended to be a mechanism for communications to systems such as ERP (enterprise resource planning), MES (manufacturing execution systems) or cloud and edge systems, according to Trask.

Another important feature of EtherCAT is its distributed clock design determinism, which contributes to the protocol’s determinism. With EtherCAT, the master device distributes a synchronized clock signal to all the sub devices (actuators or sensors controlled by another device). “This ensures that data acquisition and control are precisely synchronized across the network, even when the devices are spread out over long distances,” explains Azad Jafari, I/O product manager at Beckhoff Automation.

An appealing aspect of EtherCAT for many users is that devices on the network can be daisy-chained in line, tree, star, drop and other cabling topologies. Sub devices are connected in a series along the Ethernet cable. “This simplifies the wiring process and lowers the overall cost of the network infrastructure,” says Jafari.

Industrial application examples

EtherCAT’s fast cycle times attracts users like CMD Corp., a converting and packaging machine builder. CMD specified EtherCAT when it redesigned its 760-SUP stand-up pouch system last year. One section of the machine runs in continuous motion to feed and fold incoming plastic film while another section runs in intermittent motion to perform sealing and zipper crush operations.

The legacy control platform CMD had used on the 760-SUP had been pushed to its performance limits. “We were using the largest PLC available and couldn’t bring the PLC scan with motion below 3ms,” recalls Jason Plutz, electrical engineer at CMD. “At this point, the PLC was at 85% load.”

That platform also had a limited I/O speed. “The minimum I/O delay we could achieve was 6ms,” says Plutz.

To overcome these limitations without incurring excessive costs, CMD replaced the 760-SUP’s legacy platform with EtherCAT and Beckhoff Automation’s CX2033 embedded PC as the machine’s controller. The CX2033 runs at only 15% load on just one of the controller’s two processor cores.

Making this change also allowed CMD to eliminate a high-speed I/O module from a punching operation. In the past, a gusset punch on the continuous side of the machine required the additional hardware and excessive engineering to synchronize actuation with the position of the material. “Now, the standard I/O on EtherCAT is fast enough for our application,” says Plutz.

The improvement in performance convinced the machine builder to use EtherCAT exclusively on the 760-SUP. “EtherCAT, together with our model-based, closed-loop algorithms, enabled us to reach the fastest mold stroke motions on any injection molding machine,” says Teodor Tarita-Nistor, control software team leader. “We have mold opening-closing times below 0.5 sec, even on 600-ton and larger machines.”

Fast communications associated with EtherCAT-based systems also caught the attention of Husky Technologies, a manufacturer of injection-molding machines, molds and hot runners. The company uses EtherCAT on the control platforms for both its injection molding machines and its hot-runner systems.

Husky first adopted the technology in its production machines in 2008, adding it to the Profibus communications already in use to create a mixed fieldbus network. The goal of adding EtherCAT was to boost performance by running some parts of the machine with a scan time of 250μsec.

Massive network support

Another advantage of EtherCAT’s design is that networks based on it can be massive.

“Some fieldbuses are only strong enough to accommodate about 250 nodes before needing to add another network,” says Jafari. “EtherCAT can have up to 65,535 nodes in one network.”

The capacity to connect this many devices in a real-time, distributed control system using Ethernet at the physical layer is why EtherCAT was chosen as the backbone of the communications and control system for the Giant Magellan Telescope (GMT). When the telescope is finished being built at the Las Campanas Observatory in Chile in 2029, it will be one of the largest ground-based telescopes ever built.

The observatory’s control system will coordinate more than 3,000 axes of motion to rotate the telescope’s 22-story enclosure and adjust the position of its seven mirrors, which have a combined diameter of 25 meters.

“It’s a complex machine with thousands of degrees of freedom that need to be controlled with various levels of precision, some loose and some extremely accurate,” notes José Soto, senior electronics engineer at the GMT Organization (GMTO).

EtherCAT was selected as the GMT’s fieldbus because of its flexible topology, scalability and ability to connect a multitude of devices. A key feature for GMTO is a master sub device architecture.

“For us, the EtherCAT fieldbus can easily achieve a 2kHz sampling rate, with a large number of sub devices connected in the bus,” says Soto. “We have successfully tested about 200 sub devices in an EtherCAT ring, even implementing cable redundancy within one of our subsystems, the primary mirror.”

The architecture also streamlines collaboration among GMTO’s subsystem and instrument teams. “No matter what their designs are,” says Soto, “as long as the teams follow the EtherCAT master sub device architecture, we can integrate them with the rest of the observatory components.”

This ability helps with testing prototypes. “We can quickly set up a bus coupler and some I/Os, close the loops, take measurements and decide how we will implement the production units,” says Soto.