Is it possible to connect a Variable Speed Drive / Variable Frequency drive directly to the robot via EtherCAT?

  • Hello all,

    One customer asked me to program a couple small robot cells. He asked me to remove the PLC of those cells as they need to perform very simple operations which submit should be able to handle without hassle.

    Just in case, those robots will be KR50-R2100 and KR20-R1810-2 both with KRC4.

    Those robot cells will have 2 Variable Speed Drives (VSD from now on) each.

    Robots are brand new, in fact are being manufactured now and will be at the customer place in 16 weeks or so, I have time to prepare it all, to read as many documentation as needed and to replace the connection for analog IOs in case it is impossible.

    The best idea would be to connect those VSDs to the robot via EtherCAT, to have maximum flexibility and to avoid electrical noises affecting analog signals.

    I contacted KUKA in Spain technical support and they told me it is not possible to connect VSDs directly to the robot, but... with the right ESI (EtherCAT Slave Information file (XML from the manufacturer)) shouldn't WorkVisual be able to accept any EtherCAT device?

    I am used to connect VSDs to the PLC and there, I can configure the PDO's the VSDs will use to get and send data from/to the PLC, but I have no idea if that can be done in WorkVisual.

    My questions:

    1. Is it possible to connect a VSD directly to the robot EtherCAT bus?
    2. In case it is possible:
      1. Is there any manual I could read about it?
        1. In case receiving that manual is not legal, could you point at the manual title? I could ask it to the KUKA tech support.
      2. If there is not any manual about it, could you give me a few pointers on how to proceed?
      3. Can I modify the PDOs the VSDs are using from WorkVisual?
        1. Robot must be able to write to the VSD the following data:
          • Command (word for stop, move right, move left).
          • Desired rotation speed (word for Hz.).
        2. Robot must be able to read from the VSD the following data:
          • Status (OK, not OK)
          • Current torque (motor effort to rotate).

    As always, thank you very much in advance.


  • As I understand it, KUKA's implementation of EtherCat is only compatible with a small subset of ECat devices. It used to be that only a small number of specific Beckhoff modules were approved for use connected directly to the KRC's internal ECat bus.

    I think that list has expanded over time, but I don't think the KRC can work with any standard-compliant ECat device the way most PLCs can.

  • Hello,

    Ideally the VSD would be an Omron MX2 with the EtherCAT card 3G3AX-MX2-ECT as it's the model they use normally.

    I have attached it's ESI file (xml).

    In any case, it can be any other available drive that works with EtherCAT, that could be plugged directly to the robot and that would allow to set the speed and to read the current torque.

    Thank you in advance.

  • panic mode , SkyeFire

    I have never done this before, but:

    1. have opened work visual.

    2. File -> Import / Export -> Import Device Description File -> selected the VSD ESI / xml file and imported it.

    3. Opened an old project.

    4. Right click on EtherCAT, select Add.

    5. Search for Omron.

    6. Add it into the project.

    7. It appeared into the project.

    I understand I need to create the IO's related to what is published / subscribed into the $CONFIG.DAT (as usual) and then in the IO Mapping tab, link those variables with the Newly added device from the Fieldbusses tab.

    But I don't know how to assign the right addresses in the Modules tab...

    In 1.png you can see the PDO's I activated for that drive (the same I activated in previous projects with PLC).

    In 2.png you can see the TwinCAT configuration of the read current torque parameter (in the #x1A00 Index on 1.png).

    In 3.png you can see the Modules tab, here I see all the PDO's available, marked in green there is the 0x1A00, where I should set a value for the object to be mapped. That value should be the same one as in the TwinCAT capture.

    Any manual in which I could check about my doubts?

    Do you know how this works? a few pointers to put me on path would be more than welcome.

    Of course I will try to organize a MS Teams meeting with tech support in Spain, but given their previous answer saying this was completely impossible and that I should use external axes I am afraid this will be a dead end.

    And in case it is needed, As a reminder only:

    - Robots are brand new, still using KRC4, don't know the KSS version but I assume it will be the newest one.

    - WOV 6.0.

    And as always, A BIG THANKS for your time and help.

  • Hello Joan,


    J'ai déjà travaillé avec des variateurs de vitesse sur un robot kuka. J'ai déjà essayé de le faire avec ETHERCAT mais j'ai vite abandonné. Je vous conseille d'utiliser une communication profinet et donc un variteur compatible avec profinet. Et prenez l'option profinet m/s sur le kuka.


    I have already worked with variable speed drives on a kuka robot. I already tried to do it with ETHERCAT but I quickly gave up. I advise you to use a profinet communication and therefore a variteur compatible with profinet. And take the profinet m / s option on the kuka.

    • Helpful

    Hi all!

    Just to close this post:

    Got a "MOVITRAC B" VSD from "SEW Eurodrive", plugged it into the EtherCAT bus directly, added the ESI and it simply worked.

    Guys at KUKA Spain have done a great job assisting in the test.

    Notice: Some VSD don't work because of the special parameters in the ESI file, but, at least with SEW MOVITRAC B it works as easy as it could.

    So, point for KUKA and point for SEW.


  • I'm starting to seriously consider making a Sticky post, maybe in the Manuals sub-forum, dedicated to people listing the EtherCat modules people have gotten to work with KRC4s, and what special steps (if any) they needed to take.

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