IV: Noticeable difference in gripping accuracy between MoveL and MoveJ

unni2007unni2007 Ladenburg, Germany
As I wanted to  test the accuracy of a vision job I set up using the integrated vision of a Yumi robot, I mounted a pointing-tool to my robot and used a target with a marker.
To make sure my TCP is defined right, I aligned the tool with the world coordinate-system and rotated the wrist angle of the robot (to see if there is any change of the TCP while rotating-> there was none). I configured the quaternions of the robtarget for the grasping so that the tool is perpendicular to my gripping surface (which is parallel to the base).

While testing I noticed something strange:

If the robot approached the target with a MoveJ (using the offs command) and then moves to the target with a linear movement, the pointing tool sometimes missed the marker with an error greater than 1.5 mm, depending on the orientation of the target.
If it approached the target with a MoveL instead of a MoveJ, this error was much less.

AbsAcc is on. I also checked if something is wrong with the AbsAcc values in the MOC.cfg (and did a calibration using the calibration routine).
Shouldn't the results be comparable (within a range of 0.6 mm as this is the maximal error of absolute accuracy for the IRB14000), or am I missing something?

Thank you in advance!


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