Tool offset with external axis (linear)

    Hello,
    I would like to approach the pick point with an offset in the tool axis. So far I have done it this way.

    Code
    DECL E6POS TOffset
TOffset= {X 0,Y 0,Z -200,A 0,B 0,C 0,E1 0,E2 0,E3 0,E4 0,E5 0,E6 0}

SPTP XP1 : TOffset
SLIN P1

    But currently I have an additional linear axis and when the robot is out of range in this axis I am not able to reach it using the given method. Then I have to use the notation:

    Code
    DECL E6POS TOffset
TOffset= {X 0,Y 0,Z -200,A 0,B 0,C 0,E1 0,E2 0,E3 0,E4 0,E5 0,E6 0}
TOffset.E1 = XP1.E1

SPTP XP1 : TOffset
SLIN P1

    Could someone explain to me why I have to do it this way and make an additional record of rewriting the E1 axis value?

    Thank you in advance and best regards

    Kamil

  • MOM April 23, 2025 at 12:43 PM

    Approved the thread.
    Quote from glowny_automatyk

    But currently I have an additional linear axis

    And this axis is... where? Going by the rest of your post, I'm guessing that the robot is mounted on E1, which is probably a rail?

    Regardless: it's possible for the robot to reach a given XYZABC position in space from multiple different positions on the rail. Too many for the KRC to simply guess at. As such, it's up to the programmer to positively control all 7 DsOF.

    For a PTP move, an out-of-reach condition would be predicted before the motion began. But any LIN-stype motion consists of many, many tiny PTP motions daisy-chained together, and that reach prediction only looks one PTP motion ahead. So a LIN motion with a destination 5km distant will try to make that move, right up until it hits a joint or reach limit. This is something inherited from the original version of KRL/KSS back in the 1980s, and KUKA has probably never had any strong motive to change it.

    The FORWARD and REVERSE functions can be used in your program to try and pre-calculate this kind of problem.

    Quote from SkyeFire

    REVERSE

    Should be INVERSE.

    Or you use external offset driver to passively drag along external axis. The external offset driver offers a different redundancy solution than standard which simply is program desired external rail axis position.

    Post

    Re: Interpolation of robot mounted on external axis

    Hi,

    with the current KSS XYZABC and external axis path planning are partially independent. The external axis moves only time synched from its programmed initial positions to the target position. With the upcoming release bundle KSSV8.5/WorkVisual 5.0 there will be the new feature called External Offsets.

    If you know ABB there is also a feature called External Offsets (EOffsSet) but as far as I know this only allows statically shifting an additional axis its zero reference point. In KUKAs solution…
    Fubini
    January 2, 2018 at 12:11 PM

    Yes, it is a linear axis on which the robot is mounted and moves along with it.

    Quote

    "For a PTP move, an out-of-reach condition would be predicted before the motion began."

    So the robot controller should handle the "SPTP XP1 : TOffset" movement without completing the additional "AAA.E1 = XP1.E1" entry. The movement is from one end of the linear module to the other. After removing the above line of code, I get the message: "KR 150 R2700-2: RRS OP 118 (GetNextStep) message: Work envelope exceeded."

    In my opinion, as a programmer, I define the value of the E1 axis. To point P1, which already has some value of the E1 axis, I add 0 from my offset, so the old value should be preserved. Just like with the Z coordinate, which understands my offset.

    Is it simply that the value of the secondary axis is not offset and is treated as an absolute value?

    Thanks for your answers.

    Edited once, last by kast1337 (April 24, 2025 at 6:13 AM).

Advertising from our partners