Wireless EtherCAT over BlitzFunk®
Native EtherCAT MainDevice communication, carried over a deterministic industrial WLAN — no protocol gateway, no tunnelling, no slip ring.
EtherCAT is a wired protocol by design — so what happens when the cable itself becomes the constraint, for example on a rotating or moving part of a machine? Together with Fünfeinhalb (fuenfeinhalb.de), we have been running EC-Master over their Blitzfunk industrial wireless link to find out whether native EtherCAT, with no protocol gateway or tunnelling in between, can run reliably over the air.
EtherCAT as wired in-machine network is exactly the right thing for most machines: a cable is cheap, fast, easy to handle (install, test) and allows completely deterministic data-communication.
But as many machines include a rotating turntable, or other part that move continuously, a cable becomes the weak point right here — wear, slip rings, and cable breaks turn into recurring maintenance cost and unplanned downtime.
The topic of this lab-tests is if a wireless link could be also used between SubDevices – and thus in EtherCAT Direct Mode – which means standard EtherCAT devices, standard configuration – but using wireless links.
Supported by fünfeinhalb, acontis built up several test-setups that allow the EtherCAT MaindDvice – using the acontis EC-Master – to operate a standard EtherCAT Direct Mode network with multiple SubDevices – over a wireless link provided by fünfeinhalb's BlitzFunk devices. This allows to place the wireless link of the network between any EtherCAT SubDevices – this any part of your machine that cannot be wired can still profit from EtherCAT communication!
8 msfastest cycle time achievable |
200M+EtherCAT frames in endurance testing |
The Setup
The acontis EC-Master is operated on a standard test device at acontis – an Intel i3-9100 based PC with Intel I210 Ethernet-card running Linux with PREEMPT_RT patch.
For a simple test-setup, the PC was connected to one Blitzfunk device which acts as wireless 1:1 bridge with a second Blitzfunk device which was connected to the EtherCAT slaves – two EK1100 with some I/O slices (EL2004, EL4132, EL1004).
We tested the system with different setups – a short wireless link without any obstacles in between up to distances of approx. 15m with multiple walls (dry-walls as well as steel-enforced concrete walls).
Test setup: EC-Master on a PC with Intel I210 NIC, a Beckhoff EK1100/EL-series SubDevice stack, and a pair of Blitzfunk radios (6 GHz, channel-tested) bridging the EtherCAT link.
How it works
EC-Master, acontis' EtherCAT MainDevice (Master) stack, uses the acontis real-time Ethernet driver to access the network - exactly as it would to a cabled port. The cable runs to the BlitzFunk access point. BlitzFunk's own scheduling protocol reserves a fixed time slot for the link in each direction – this allows to guarantee a fixed latency per frame-transfer. EtherCAT frames pass through the radio link natively — there is no protocol conversion, no standard store-and-forward gateway.
As the BlitzFunk devices are transparent to the network there is also no change to the ENI configuration needed, neither any specific configuration or modifications at SubDevice-level, nor the application above EC-Master. From the master's point of view, the wireless hop behaves like an extra, well-characterized piece of cable with a fixed delay.
With BlitzFunk's current firmware, that fixed delay is 4 ms guaranteed per direction, which is why 8 ms is the fastest EtherCAT cycle time the link supports today. Everything above 8 ms — 10 ms, 20 ms, and slower — runs with comfortable margin.
Measured performance
We ran EC-Master against BlitzFunk in long-duration endurance tests at distances from about 1 m up to 15 m, including runs through several walls (dry-walls and steel-enforced concrete walls), at a conservative 10 ms EtherCAT cycle time, with round-trip time and frame loss measured continuously over 24- to 72-hour windows:
Scenario |
Distance |
Duration |
Frames sent |
Frame loss |
Avg. round-trip |
|
A – short range |
~1 m |
72 h |
51.84 M |
0.077 ppm |
3.6 ms |
|
B – mid range, no walls |
~10 m |
24 h |
17.28 M |
1.2 ppm |
4.9 ms |
|
C – larger distance, through walls |
~15 m |
24–72 h |
17.28–51.84 M |
0.06–5.1 ppm |
3.4–5.1 ms |
Frame loss stayed in the low single-digit to double-digit parts-per-million range across more than 200 million transmitted frames in total, and round-trip times stayed well inside the 10 ms cycle even at 15 m through walls.
We also checked the error ratio based on daytime, and the operations within the acontis office did not have significant effects on the error rate.
Frame loss per hour over a 72-hour endurance run at 15 m distance — isolated single-digit losses per hour, no systematic drift
Stable communication even with challenging environment.
During testing we used the Blitzfunk configuration tool to check and optimize antenna alignment and stability of the connection to ensure a stable wireless link.
To verify that the system provides stable communication even in challenging environments, we also added a verification test – with 15m distance, concrete and dry walls as obstacles and deliberately suboptimal antenna alignment to artificially impact the stability of the wireless link. This resulted in some increased error rates (up to 33 ppm), but the EtherCAT communication itself was still running stable at decent cycle times.
When repeating the same setup with correct antenna alignment (but with same device placement – 15m distance, concrete and dry walls as obstacle) we measured a significant lower error rate down below 0.2 ppm!
Thus, in practice the link quality is a matter of correct installation, but likely not a hard physical limit – and to run stable EtherCAT communication a stable link is key. Therefore, the installation needs to be checked with the Blitzfunk configuration and monitoring tools before using it productively.
Conclusion
The measured results are really promising: We could achieve stable EtherCAT communication with a stable round-trip time and low frame losses. In fact, the current setup seems feasible for field-use with 10ms Cycle times and higher – allowing unknown flexibility in terms of SubDevice placement in machines, as slip-rings and such can be simply replaced by a 1:1 wireless link.
10ms might seem slow for many working with high-speed motion applications; but in many use-cases, the in-machine network is way slower – 10 or 20ms cycle times still provide much faster data-transfer and significant better synchronicity of all devices than classic fieldbusses like CANopen or Profibus can achieve.
Note: fünfeinhalb continuously works on new firmware which provide even lower per-direction latency – providing outlook to even faster cycle times in near future.
Typical applications
The possibility to use wireless communication within EtherCAT can be beneficial in many use-cases where cables were so far limited – either due to mechanical or environmental limitations of Ethernet-cables.
- Rotary tables, turntables and slip-ring replacement — eliminate wear parts on continuously rotating axes.
- Moving tool heads — avoid cable flexing and connector fatigue at the moving interface.
- Hard-to-cable retrofits — add EtherCAT SubDevices to existing machinery where running new cable is impractical.
- Environmental conditions that limit the use of cables – e.g. due to chemical cocktails affecting cables.
- Temporary and reconfigurable setups — test cells, event and stage automation, and machines that are frequently re-laid-out.
Related Products
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TECHNOLOGY PARTNER fünfeinhalb — BlitzFunkBlitzFunk, made by the German company fünfeinhalb, is a deterministic industrial WLAN built for moving machines, mobile robots and safety-related control. A proprietary scheduling protocol reserves airtime for every device in advance, so latency and data rate are fixed worst-case guarantees rather than best-effort averages — exactly the property EC-Master needs to carry real EtherCAT traffic over the air. BlitzFunk runs in the 2.4 GHz, 5 GHz and the still largely unused 6 GHz band, supports seamless roaming between access points with no added latency, encrypts and authenticates all traffic by default, and is configured through a web interface in about a minute. Visit fünfeinhalb → |