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Reorientation Problem

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Resident
Resident ✭
in Robot Controller
Hi

I'm having trouble with my robot (IRB140). When I jog the TCP by orientation, in some arm poses the TCP will visibly deviate from position, yet the jog window will indicate that the x,y,z position has stayed the same. This is not a case of a bad tool definition as about 75% of the time the TCP point does not deviate.

I have updated the rev counters and this has not fixed the problem. Has anyone come across this? Is it a case of a bad fine calibration in one of the axis that is forcing the TCP to move when that axis comes into play during reorientation?

Any help is appreciated.

-- David 

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  • Resident
    Resident ✭
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    I should add that I just removed all the tooling and even at tool0 it appears to deviate. 
  • graemepaulin
    graemepaulin mod
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    Hi,
     

    Have you checked to calibration offsets in the motor calibration system parameter match those on the label on the back of the arm?

     

    Regards

    Graeme
  • Resident
    Resident ✭
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    Yep, checked that.
  • graemepaulin
    graemepaulin mod
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    Have you sent the robot to its calibration postion with a MoveAbsJ command and checked it lines up on the calibration marks?

  • Resident
    Resident ✭
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    Not exactly, but when I was checking the rev counters, I jogged them all to 0 +/- 0.5deg and they lined up. Is it worth doing what you said anyway?
  • Resident
    Resident ✭
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    I should probably mention that the robot is hanging upside down, however I have set the alpha angle (or beta, which ever the manual said) to 3.14159.
  • graemepaulin
    graemepaulin mod
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    Yes you should check it with the MoveAbsJ, all the marks should line up exactly.
    If they do not (and the calibration offsets are correct to the label) the robot needs to be fine recalibrated.
  • Resident
    Resident ✭
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    Is this axis (axis 3 on an IRB140) lined up? The manual is fairly confusing on this axis.
  • graemepaulin
    graemepaulin mod
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    Yes that is correctly lined up (the two machined surfaces should be in line). graemepaulin2011-05-13 04:07:47
  • samatsimt
    samatsimt ✭
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    How much of a deviation is considered 'good enough'? I have done TCP definitions with very small error (max min mean) and yet the tcp still deviates visibly to around ~1-1.5mm. Should that be acceptable?

    Yes I checked that the calibration offsets are same as the label and MoveAbsJ to home position aligns the markings perfectly. Is fine recalibrated something that the a end user (novice or expert) can do? Or is service from ABB actually required?

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