KUKA Robot: Drives not turning on in certain cases of EXT Mode operation after user safety is turned Off and then ON

    Hi,

    I am working with a KUKA KRC5 controller communicating via PROFINET with a SIEMENS PLC with Profisafe enabled. I have Safety hardware programmed in my PLC logic which is connected to the Profisafe tag of the robots. I have no problems in communicating and controlling the robot in safe mode.

    I am running into a random issue. When a subprogram is running and the Operator Safety is disabled (by opening Safety Door Lock) the robot pauses at it should. But after re-enabling Operator Safety. In some cases, the robot continues its program from where it had paused after Confrim Message signal is passed onto the robot. There are no issues. But at some specific points in certain subprograms, the robot doesn't resume operation after re-enabling safety since the Drives don't turn on. In that case, after Confirm Message, Robot has Control Ready active but Peri_RDY is not active and drives of robot are not on. In these cases the program on robot is stuck in error mode.

    I have been unable to find a pattern or reason why it happens for some parts of a program and not for others. My safety integration has no other issues and without operator safety being disabled in Aut_EXT mode, the robot runs very smoothly with no errors.

    Can someone please help with this?

  • massula December 13, 2024 at 1:14 PM

    Approved the thread.
    Quote from mihird

    When a subprogram is running and the Operator Safety is disabled (by opening Safety Door Lock) the robot pauses at it should.

    Operator safety is tripped and will need to be acknowledged later on before process can resume

    Quote from mihird

    But at some specific points in certain subprograms, the robot doesn't resume operation after re-enabling safety since the Drives don't turn on.

    robot cannot move unless drives are on. in EXT mode robot is controlled by PLC. so it is the job of PLC to check if the drives are on or not. and it is PLCs job to turn them on... this has nothing to do with robot programs/subprograms. it does not matter if some robot program is selected or not. turning on drives is completely independent of robot interpreter state.

    Quote from mihird

    after Confirm Message, Robot has Control Ready active but Peri_RDY is not active and drives of robot are not on.

    PLC has to turn on Move Enable, and Drives Off signals... and then pulse on Drives On signal. and if needed pulse it again until drives are on... because Drives On input is edge sensitive. this means it responds to transition and not level of the signal. and this means that to see rising edge, Drives On first must be off...and not just off but off long enough so that robot sees that signal is low... KUKA used to state somewhere that this need to be at least 20ms. but even that may be too short. fieldbus alone may have RPI of some 10-20ms. then you have interpolation time of Submit that is 12ms... and PLC has scan time that may be 10-50ms... and all of those delays add up... so PLC programmers need to be aware of those things... i usually make it 50-100ms. because if PLC does not keep Drives On signal low long enough, robot may not see the rising edge... then you are stuck...

    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

    This makes sense. I have to add a pulse logic to the Drives ON command. Maybe it is the difference in scan times of the robot controller and PLC that the edge is not getting detected as it should be. As for the Operator Safety Acknowledged point, I have not needed to do the same yet. It works automatically for me. But I will try it nonetheless.

    Thank you. I will try this.

    panic mode The pulse idea worked like a charm. I used a TON delay to turn on Drives ON after Drives OFF.

    I increased the delay for turning Drives ON to 200 ms just to be safe. After confirmation of Operator Safety.

    Now in any situation with a Confirm Message enable the robot resumes the program.

    Thank you for the solution. Hadn't realized that the positive edge detection could've been the issue.

    i know...

    Post

    Re: Understanding cell.src

    Hello,

    There are three types of PGNO, all are well docummented.

    For few programs type 3 may be simpler (specially if using wired signals between PLC and KRC). Note that control sequence is a bit different though...

    things to watch for is signal type - Some signals are EDGE-SENSITIVE, while others are LEVEL-SENSITIVE. this is a very important distinction. edge sensitive signals in this case are rising-edge sensitive. this means that if the signal is already true (or is not low long enough) edge may…
    panic mode
    May 18, 2018 at 5:53 PM

    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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