How to integrate custom external axis into KRC4 compact setup - first steps done !

  • Hi,

    I do have a servo motor driven harmonic drive with a matching Ethercat servor driver. I want to use it as a light turntable E1 for my KRC4 compact. The servo drive runs commonly used DS402 protocol.

    The final goal is to really control the turntable as E1. It there a way to configure the robot in workvisual to use a 'foreign' Ethercat servo driver for an external axis?

    My successful approach so far:

    I configured a Kuka external axis from the catalalog as simulated E1 in workvisual. I modified the submit task to read the current simulated E1 position and send it as new target position to the E1 servo drive. That works perfectly fine for indexing the workpiece and procees milling. All good.

    For synchronous ( A1 to A6 and E1) moves the non-predictive characteristics of the submit excecution leads to unwanted artefacts. I really want to get rid of them.

    Did you go any further than that? Do you run a KRC4 compact with kuka External axis? How ist the setup there?

    Am I on the wrong track? Is it impossible to go any further, because Kuka made it impossible?

    I really appreciate any input on that topic.

    Thanks a lot,


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  • SkyeFire

    Changed the title of the thread from “Who to integrate custom external axis into KRC4 compact setup - first steps done !” to “How to integrate custom external axis into KRC4 compact setup - first steps done !”.
  • Hi, designingB
    I'm doing a project similar to yours: using an EtherCAT motor driver as an external axis. Yet I'm afraid I can't provide any solution for your question as I'm still stuck on the first step.

    Could you please provide part of your modified SPS where you send the target position data to the EtherCAT slave? Or, any hint of which syntax to use will be very helpful.

    My setup: KSS 8.3.42, KRC4 and KR300 R2500. The motor is a stepper provided by Oriental Motors and it comes with a EtherCAT-enabled drive.

    I have no idea how EtherCAT work and how a KRC communicate with a EtherCAT slave.(CWRITE?)
    PLC, etherCAT, automation are all whole new topics to me, and I'm trying to learn them from scratch. Kuka's manual for EtherCAT on KSS 8.3 provides no syntax example. The EtherCAT manuals provided by Beckhoff are very comprehensive but I need time to read them through. New terms and concept keep popping up and I need to google them one by one.

    Any code snippet that can help me narrow down the keywords to study is very appreciated.

    I think I have done the required physical wiring as I can jog the motor with the vendor's motor setting software. The ESI file is imported and added to the work visual project, and the topology of the EtherCAT devices match the physical wiring (I wired the EtherCAT in port of the motor drive with the EtherCAT out port of the EK1100, and the EK1100 and its neighbor blocks are already working properly).

  • SPS is not just asynchronous with respect to robot interpreter but it is also a low priority task. one could make some workarounds. for example try to maximize CPU quota for the specific submit interpreter. if that is not enough, do milling only while E1 is stationary. if E1 need to be synchronous use proper KUKA axis or at least ConveyorTech to track E1.

    1) read pinned topic: READ FIRST...

    2) if you have an issue with robot, post question in the correct forum section... do NOT contact me directly

    3) read 1 and 2

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