Key development tools and standards ensure full interoperability among the massive variety of EtherCAT devices and manufacturers
Selecting the right communication technology is one of the most important decisions engineers make. In many ways, this consideration is even more important than the machine controller. Fieldbus communications directly determine whether the field devices can match the controller’s performance and which devices can be used. This article, the fourth in a year-long series of articles about EtherCAT, will talk about how fieldbuses enhance or harm interoperability depending on which you choose.
The EtherCAT Technology Group (ETG) takes conformance and interoperability of devices seriously. Facilitating interoperability among all devices is complex and requires diligence on the part of the trade organization. The ETG’s motivation is not to gather licenses, agreements, or members, but to ensure proper design, development, and successful use of EtherCAT devices.
Device interoperability is one of many areas where EtherCAT shines. There are two primary reasons why.
First, there is only one EtherCAT protocol version. You read that right: There are not multiple versions of EtherCAT. The EtherCAT technology has never changed, it has just been enhanced. Having a stable base specification means new devices can be used in existing systems without problems and without version control concerns. It also provides a firm foundation for EtherCAT extensions, including Safety over EtherCAT (FSoE) for integrated functional safety, EtherCAT P for power and communication in one cable, and EtherCAT G/G10, which provide 1 Gbit/s and 10 Gbit/s communication rates, respectively. There will continue to be more enhancements in the future, but again, they will not change the base technology of EtherCAT Version 1.
The second primary reason for ensuring interoperability is the ETG member policy surrounding conformance. It is the obligation of all EtherCAT device vendors to follow the ETG conformance policy.
Together with exceptional performance, flexible topology, simplicity and robustness, safety, affordability, openness, and so on – the promise of full interoperability results in a large number and variety of EtherCAT vendors and devices.
The Conformance Test Tool (CTT)
The CTT is an in-house test of EtherCAT devices as well as a powerful development tool. An EtherCAT device developer can run the CTT during development to catch possible interoperability issues well in advance of market release. This is like compiling your code often: It’s best to identify issues early and fix them right away rather than merely compiling code at the end only to see problems pile up.
All developers of EtherCAT devices are required to maintain a subscription to the CTT. The tool is continuously refined to accommodate industry-specific test cases and enhancements to the base EtherCAT specifications. Legacy fieldbus systems used to suffer – and still do – from static testing mechanisms that became outdated very quickly. Early on, ETG members decided to have a continuously updated conformance test tool.
All EtherCAT device vendors are required to have their EtherCAT devices pass a Conformance Test before releasing them to the market. The test results do not have to be submitted but must be available upon request. The CTT, combined with the commonality of the EtherCAT Slave Controller (ESC), strives to ensure that EtherCAT devices you purchase will always work with your network architecture and not adversely affect its performance, reliability or functionality.
EtherCAT Test Centers
An optional conformance check can be done at an EtherCAT Test Center. CTT results are checked along with verifying proper exterior markings and LED handling, which cannot be determined by the test tool. It is common for end users to request a vendor to perform an optional conformance test at a recognized EtherCAT Test Center.
There are five EtherCAT Test Centers around the world, including a North American site in Minneapolis. The results of the optional test are secure, and after completion, vendors can advertise successful completion of the optional test.
FSoE Conformance Test
While commonly known as Safety over EtherCAT, FSoE literally stands for Fail-Safe over EtherCAT. FSoE provides a mathematically verified safe communications channel over EtherCAT and meets the standards to transfer safety data reliably and in a very timely matter. With FSoE, functional safety features such as door interlocks, e-stops or safety drives can communicate over the same communication system that also handles all the other process data. This is another signature feature of EtherCAT. There truly is an open safety communication standard available.
The ETG has streamlined the process for FSoE compliance and conformance assessment, including working directly with a so-called notified body, which eases the burden on the vendor. There are safety controllers and safety devices from more than 40 vendors. Users can pick and choose the best safety device for their application without worrying about interoperability between devices. This is quite unprecedented in safety circles where users are largely constrained to a single vendor for safety components.
EtherCAT PlugFests
PlugFests are my favorite. And they parallel omnipresent standards like USB. Put many EtherCAT devices in a room with various EtherCAT controllers and hook them up. There are always EtherCAT Conformance Test Tool experts on hand to answer questions. During the event, all EtherCAT devices are connected to the participating controller offerings. At the end, all EtherCAT devices are connected – it does not matter how – and each EtherCAT controller is connected to the overall system. By that time, all devices are in place and working in harmony. It never ceases to amaze me how well this goes.
Conclusion
Any fieldbus or communication technology is useless without viable interoperability. EtherCAT has a solid reputation for offering easy-to-integrate field devices that work with a variety of controllers. This is not by accident. You can move forward with EtherCAT devices from many different vendors without worrying about how they will work together. We all benefit as a result.
Want to learn more about complete interoperability in industrial networking? Contact ETG or your local Beckhoff sales engineer today.
Robert Trask, P.E., is the North America Representative of the EtherCAT Technology Group.
A version of this article previously appeared in Control Engineering. It is republished here with permission from ETG.