Do anyone know what is the accuracy and repeatability of KUKA KR5 arc with KRC2 controller. The technical manual says repeatability is +-0.1mm. But according to ISO 9283 repeatability is given by an absolute value(without +-). Also the speed and loading conditions are not given in the manual.
Experimentally I have got minimum repeatability values of around 0.20mm and minimum accuracy of about 0.91mm for planar motion at 30% speed and less than 5Kg loading(lesser than maximum loading condition). This was done using camera mounted on robot end effector.
Do anyone have experimental results for KUKA KR5 Arc ACCURACY and Repeatability?
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riby -
February 9, 2013 at 10:50 AM -
Thread is marked as Resolved.
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Repeatability and accuracy can be measured in different ways. Robot manufacturers tend to define it in +/-, what amounts to the error "radius." Others use the "diameter." And then there's "True Position," which... I forget the exact formula, but it's actually smaller than the "raw" accuracy.
As far as I recall, KUKA accuracy callouts are specified for the robot's default payload (actually, there should be a footnote in the document that details this). I'm surprised that you're getting repeatability that's less than the document -- generally I've found the written accuracy figures to be worst-case numbers.
Have you set up your load data correctly? That can definitely have an effect. Also, on lighter robots like the KR5, tension in cabling and hosing along the arm can have exaggerated effects on repeatability and accuracy.
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The technical manual says repeatability is +-0.1mm.Usually the repeatability RP of a KUKA robot (Fanuc, Motoman, ABB as well) is much better than 0.1 mm (error radius, not +/-). Often the measurement systems are not accurate enough to measure the robot's repeatability Additional it is difficult to measure the repeatability, but not some kind of thermal drift.
But according to ISO 9283 repeatability is given by an absolute value(without +-). Also the speed and loading conditions are not given in the manual.KUKA uses according to ISO 9283 the default payload and 100% speed.
... minimum accuracy of about 0.91mm ...With an absolute accurate KUKA robot (with correct load data) the mean value of the pose accuracy should be smaller than 0.7 mm, typically 0.5 mm (according to ISO 9283, i.e. ISO cube but not the whole workspace). If the robot is not absolute accurate the pose accuracy may be up to some millimeters.
... for planar motion at 30% speed ...Riby, maybe you have measured the path accuracy AT?
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SkyeFire: Can you please direct me to the documents where the formulae for accuracy and repeatability is documented(Other than ISO 9283 document).I have found that there are two measures of repeatability. One is ISO 9283 and the other is based on ANSI standard. ISO formula is RP=Lbar+3SL(http://blog.robotiq.com/bid/36551/Robo…and-Measurement). Whereas ANSI states that Lbar value is sufficient(Handbook of Industrial Robotics, Volume 1 By Shimon Y. Nof). In that case the values the minimum repeatability according to my measurement is .06mm; much within the specifications.
Anyways I suspect the original expression has a problem in mathematical sense because only 3*SL is sufficient to express the radius of error.(Like the 3 sigma concept). Perhaps I need to read a better ref manual.
I have not used kuka load I will try it and redo the experiment. I have just downloaded it and figuring out how to use it.
Puck: Another concern is that I have a camera system with lenses such that 1 pixel=.03mm. I can use better optics to further reduce it to the order of few microns on a planar surface.
Repeatability of KUKA KR5 arc with KRC2 controller is +-.01. Whereas for the new version of controller it is +-.04mm. We have the older version and thus it should be +-0.1mm.
30% speed was the velocity of traverse from point to Point of during measurement. Measurement was made only after the robot motion had ended. I could find that the repeatability becomes worse with increase in this speed. I don't have absolute measurements for the same. -
There's a footnote in the spec document here: http://www.kuka-robotics.com/res/sps/e6c775…KR_5_arc_de.pdf, but all it says is that the measurement is to the ISO 9283.
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I have now results of accuracy by making measurements using Laser Tracker. It is about 1mm after optimizing the errors due to teaching base and tool. Overall considering base as well as tool teaching it is about 2mm (region closest to origin of robot world coordinate frame - retracted position) to 4mm at the extreme region of workspace (Extended robot pose).