Ethernet for Control Automation Technology (EtherCAT) is a real-time Industrial Ethernet technology. An update from industry experts reveals an industrial protocol with a continuing technology focus on its roots: short cycle times (≤100 µs), low jitter for accurate synchronization (≤1 µs) and low hardware costs.
EtherCAT automation, motion and machine control solutions have been a stalwart piece of the Industrial Ethernet networking ecosystem for nearly 20 years.
For the IEB Special Report on EtherCAT, the Industrial Ethernet Book reached out to Dr. Guido Beckmann, Senior Management Control System Architecture & International Key Accounts at Beckhoff Automation and Martin Rostan, Executive Director at the EtherCAT Technology Group to provide readers an update on this key Industrial Ethernet technology.
What key technical trends are driving the adoption of EtherCAT automation, control and networking solutions?
Dr. Guido Beckmann: Performance, ease of use and low cost were the goals when we developed EtherCAT in the early 2000s. Performance, because the Lightbus, which we introduced to the market in 1989, no longer matched the performance increase of PC-based control technology: Beckhoff is, after all, the pioneer of this approach and has been using PCs as industrial controllers since 1986. Ease of use, as we were accustomed to with the Lightbus; just plug it together, without having to set addresses or configure switches and routers. And low costs are of course always desirable – in this case, the low hardware costs and the simple handling, which saves commissioning costs, work together ideally. And this then supplemented by real openness.
That’s why we opened EtherCAT to everyone, together with 32 partner companies founded the EtherCAT Technology Group in 2003 and thus contributed to EtherCAT become a leading bus technology. And these goals were not only important at that time, but they are also still technical trends today, followed by customers and manufacturers of automation solutions alike. EtherCAT is at its best at the lower levels of the IoT and Industrie 4.0 architecture: wherever hard real-time, flexible topology or low costs are important.
Martin Rostan, ETG: The mega-trend leading to EtherCAT as the bus technology of choice has been around for years, and away from proprietary PLCs and towards PC-based control technology. This means that computing power is no longer a limiting factor, and a bus technology is needed that can cope with very short cycle times and does not represent a performance bottleneck. Users are realizing that bus systems cycle times in the range of milliseconds do not suit controllers that control in the sub-millisecond range.
EtherCAT is not only by far the best-performing Industrial Ethernet technology, but also the only one that enables hard real-time without any hardware extension in the control PC: a standard Ethernet port, as it is already on board every industrial PC, is completely sufficient with EtherCAT. Thus, EtherCAT not only saves costs, but also ensures openness: you are no longer bound to the hardware of one manufacturer.
The EtherCAT Device Protocol with its unique functional principle of processing on-the-fly is particularly well suited for networking controllers with I/Os, drives, sensors and alike. It is supplemented by the EtherCAT Automation Protocol for networking controllers with each other, which is classically switch-based and uses existing Ethernet infrastructure.
What are the key technical advantages of automation systems that utilize EtherCAT technology solutions? What are its primary technology benefits for automation and control networking?
Dr. Guido Beckmann: In addition to the above-mentioned performance paired with very easy handling of the system, our customers appreciate the complete freedom in network topology: Practically any number of nodes can be connected in a line without sacrificing performance due to integrated switch chips. Drop lines, tree and star topologies are also possible, as is line redundancy for applications with high availability requirements. For the latter, special devices are not even needed: every EtherCAT device with 2 ports supports this. The performance is perfectly leveraged by our special high-end I/Os with time stamping and oversampling, even overcoming the limits of cycle times. With just one click, the user can see not only the network topology and all the devices used, but also whether there are connection problems or disturbances anywhere – and without having to know the network or the application beforehand and again, every EtherCAT device supports this by default.
And of course, Safety over EtherCAT plays an important role for more and more customers: seamlessly integrating functional safety into the system is an important benefit of EtherCAT. The Beckhoff TwinSAFE solution is based on Safety over EtherCAT and supports the integration of safety devices from the broad range of available products from different vendors.
Martin Rostan, ETG: The most important technical advantages of EtherCAT result from its unique “processing on-the-fly” principle. Instead of sending a frame to each network node in each cycle and receiving a response frame from each device, the controller sends a frame through all nodes, which read the output data intended for them and insert their input data. This not only leads to perfect bandwidth utilization and thus to the exceptional performance of EtherCAT, but also simplifies the system enormously. Manual address setting is not necessary, neither are routers, switches, and their configuration. Any topologies are possible without the limitation of cascaded switches. Bit errors and even loose connectors are not only detected but also localized, which drastically simplifies troubleshooting.
And because EtherCAT is not based on the Internet Protocol and the EtherCAT chips filter out all other traffic, the user does not have to worry about cyber security either. In addition to the technical advantages there are the strategic ones: EtherCAT has never been changed, only extended in a completely downward compatible way. This means there are no versioning problems. And because EtherCAT is also truly open on the controller side, the user can choose from by far the largest variety of devices on the market.
What is the impact of SPE and/or Ethernet-APL cabling and network topologies on the types of network architectures that are possible? What are the advantages of these new approaches?
Dr. Guido Beckmann: Single Pair Ethernet is sometimes misleadingly portrayed as a new bus system or an IoT enabler. SPE stands for several Ethernet physical layer variants, which were originally developed for in-vehicle applications, which is why it was initially only intended for very short cable lengths. Then the extension for long lines started, but so far only for 10Mbit/s and Gb/s. We are actively accompanying this development in the IEEE. We see an influence on the network architectures in automation technology mainly where 100m between two nodes is not sufficient – e.g. in large process plants, and there then with 10Mbit/s. APL was derived from 10Base-T1L and enhances this with power and intrinsic safety. For EtherCAT and 100Mbit/s for quite some time we have devices, which allow up to 300m cable length between two nodes.
Martin Rostan, ETG: SPE is a set of physical layer alternatives for Ethernet that can lead to longer cables between two nodes at 10 Mbit/s and 1 Gb/s, and shorter cables and higher costs at 100 Mbit/s. Therefore, SPE is not a reasonable alternative for EtherCAT. IEEE is about to start a project to specify longer cables also at 100 Mbit/s, but this will take several years. Ethernet APL combines 10 Mbit/s with power over the line and intrinsic safety, and that is incompatible with SPE using Power over Data Line (PoDL). APL may be interesting for slow process applications, although it is often overlooked that APL is specified for different cable than those currently installed in chemical plants. This is likely to become a challenge, at least at longer distances.
What are specific application areas are the newest EtherCAT solutions targeting? How are these solutions contributing to IoT and enterprise connectivity?
Dr. Guido Beckmann: EtherCAT was designed from the outset to be so universal that the technology is suitable for a very wide range of applications. Of course, many use EtherCAT for particularly demanding applications, in terms of cycle time, synchronization accuracy and throughput. This is why EtherCAT is also the leading bus system for all types of motion control, and an ideal fit for advanced motion solution such as our XTS linear transport system or the new Planar motor system “XPlanar”. But the simplicity of use, the flexible topology and last but not least the low costs lead to the situation that EtherCAT is also very well established in many applications where performance is not important at all. And combining EtherCAT with the TwinCAT connectivity solutions is the perfect fit for any IoT application: extremely fast data acquisition via EtherCAT together with any Ethernet based protocol, including but not limited to the EtherCAT Automation Protocol, OPC UA or MQTT.
Martin Rostan, ETG: With EtherCAT G, we will have an extension of EtherCAT which will offer even more bandwidth. The focus is not on even lower cycle time, whereby this is achieved along the way. Larger bandwidth than 100Mbit/s is needed for example for certain measurement applications with high sampling rates or cameras with live stream. With the EtherCAT Branch Controller technology, it will be possible to combine 100Mbit/s segments with network segments of higher data rates, thus keeping the robust and cost-effective 100Mbit/s technology where it makes the most sense: in the harsh machine environment.
Thanks to parallel processing of the segments, this even leads to significantly better performance while retaining the existing devices. At the same time, devices with higher bandwidth requirements can benefit from the higher data rates. EtherCAT G will therefore not replace the 100 Mbit/s technology but complement it. And EtherCAT is thus prepared for the future: EtherCAT will remain the fastest Industrial Ethernet technology in the long term and will still be the bus system of choice in 20 years. And the combination of the EtherCAT Device Protocol southbound of the controller together with the EtherCAT Automation Protocol or OPC-UA – depending on the requirements – north of the controller is the ideal solution for IoT connectivity.
What are the engineering challenges that the newest EtherCAT systems and architectures are designed to address, and how is EtherCAT evolving to provide more comprehensive solutions?
Dr. Guido Beckmann: One of our latest EtherCAT based systems is the planar motor system, XPlanar, which combines the advantages of conventional transport technologies with magnetic levitation. The levitating 2D product transport enables a wide range of new options for handling products within a machine and also between several machines. The user benefits from the freedom of movement of the object carriers: Individual goods can be transported to any location via any route. XPlanar combines this flexibility with the dynamics of conventional linear motors and offers added value through cycle-time-optimized linking of individual production steps.
Since in XPlanar systems we also close the control loops in a central PC to enable the best coordination of the movers, we need very short cycle times with maximum data throughput. Therefore, EtherCAT G is already used in these systems. A brand new EtherCAT based product is the MX-System. This is a uniform modular automation component that can be used to completely replace traditional control cabinets with modules in many applications. The MX-System consists of a robust aluminum baseplate in protection class IP67 with integrated module slots that feature EtherCAT for communication and an integrated power supply. EtherCAT forms the technological foundation for the standard interfaces of the MX-System. As EtherCAT covers the entire range of data transmission requirements, one bus system is sufficient for internal system communication as well as for external expansions, which can also be connected via EtherCAT P – the One Cable Automation extension of EtherCAT technology.
Martin Rostan, ETG: One of the toughest engineering challenges is to unlock new possibilities without having to accept technology disruptions: Continuity and stability are more important than disruption to users who need to keep a production plant running. That’s why we have never changed EtherCAT, but always extended it carefully, prudently and completely backwards compatible: there is only one version of EtherCAT, and that will not change with EtherCAT G either.
And so with EtherCAT, you can add a new device to an old network without having to worry about the protocol version. And at the same time with EtherCAT you get the benefit of new enhancements to meet new requirements, as it is the case with EtherCAT G. The feedback from our members, both from the user and vendor side, shows that this approach is highly appreciated and is, in itself, a good reason to rely on our technology.