I have an piezo motor application that is displaying problematic behavior under closed-loop control for some (not all) axes.
The system is a Geobrick LV (NSLS-II) outputting step/direction to six MiCos PMC-100, which drive nanopositioner stages (stick-slip piezo). Feedback is via a MicroE incremental linear encoders ( 0.005 um resolution).
I myopically tuned all 6 axes of this system for small moves (0.25-5 um), as that is how it is used in practice. On further investigation, 3 of the 6 axes trip on fatal following error for longer moves, but only in one direction (Ixx11 = 32000) . The other direction is fine. The problematic axes trip on this error a fraction of a second after a commanded move (J+/J-, etc), regardless of Ixx22 setting (jog speed).
Gravity is not an issue here as one of two of the vertical stages works fine in closed-loop.
Is there any way to tune for this type of behavior? I'm kinda at a loss here...
Thanks.