Limits of base calibration

    Kuka KR6 r900

    KSS 8.3

    I have been doing some experimentation with the base calibrate function on the above robot... Its a handy tool for the process I am working on, so I am trying to get a better understanding of it.

    Its easy enough to shift the base 10-20mm and re-calibrate. The basic script I am using will work fine with these minor changes.

    However, shifting the base to a new quadrant does not seem possible so far. I have tried adding intermediate points, but every time I will get a software limit error, and the robot will not move.

    Does anyone know if the base calibration designed for these large shifts? or only minor adjustments?

    Thanks!


    rob.

    Define what you mean by shifting a base to a new quadrant? are you using the geometric operator to shift your base?

    If by shifting your base to a new quadrant you mean going to a position where you are basically working on the other side of robot, you can not just shift your program linearly, you also need to either rotate your base or your tool orientation.

    Every problem has a solution, that isn't the problem. The problem is the solution.

    Hi Leon,

    Apologies if that was not clear - but yes you are correct. if the base was on the right side of the robot, I have moved it over to the left. No geometric operator.

    By re-calibrating the base, am I not defining it's rotational orientation? I am using 3-point. Defining the origin, X and Y axis.

    I am using PTP only, and all poses are defined using the base as a reference.

    Oke, that makes things a little clearer, now i am thinking about how to explain this only by text.

    I have run into this same problem myself and there are a few ways around it.

    I use my robots only for milling so when i only have to do 2D work in choose the tool orientation Where the flange of A5 is aligned with one axis (x or y). this way you can always shift your base linearly over that same axis. So in my case for 2d work this is always the X-axis and i can move from x-1500 to x1500 and y from 0 to 1500. If i need to be on the other side i have to rotate the base by 180 degrees and then everything is fine.

    When i have to mill 3d objects or just simple multiple faces. Basically programs where you can not keep your tool orientation the same, i Always rotate the base when i have to move it to a different table (my setup has 6 different worktables in a circle round the base of the robot). So again in my case if move from 1 corner to the other for example x-1200 to x 1200, rotate the base by 90 degrees around z. This ensures that the biggest changes is basically A1 and the rest of your axis positions and the robots pose stays the same en thus preventing you from getting software limit errors or axis limit errors when shifting a base.

    I hope you can make some sense of this. It is not my most clear explanation but i dont have time to make some simple pictures to explain it better. Basically your problem is tool orientation and you have to mindful of it when shifting bases through different quadrants.

    Every problem has a solution, that isn't the problem. The problem is the solution.

    "Software limit error" -- what error, specifically? On a LIN or PTP motion? Is the wrist trying to flip over, or the elbow trying to invert?

    If it's a limit on A4 or A6, you may be running into S&T issues. If you're using LIN motions, I suspect that your original points are programmed too close to the A5 singularity.

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