Stephen Wille Padnos wrote: > Roger wrote: > > >> > If a step motor loses a step due to excessive loading, then it's likely > to miss many steps. The one motor will be stalled while the software > ramps the speed down on the other joints, so the part is already likelly > to be ruined. At some random time, the stalled motor will start moving > again, but it's trailing the position it should be in. The motion > controller can't speed the motor up to catch up to where it should be > (ask it for a little more, like you'd do with a servo), since it's > already at or beyond its limits or it wouldn't have stalled in the first > place. > > >> Not perfect but maybe good enough. >> > Could be. This has been discussed at length, both here and by various > Geckodrive folks. EMC2 has the ability to get feedback, and it has the > ability to apply feed rate overrides in realtime. If you can figure out > an algorithm to marry the two to get pseudo-servo steppers then I'd be > happy to review your code - patches gratefully accepted ;) > Before I used the original EMC, I had an Allen-Bradley 7320 control, a 1978 vintage, 16-bit minicomputer. It had a feedrate compensation scheme. If any axis exceeded a first threshold of following error, it would reduce feedrate to 50% of commanded F value. When the error was reduced, it would go back to 100%. When this happened, my Bridgeport would start rocking like a bobble-head! It was quite comical, but not something I liked to see! I think the coupling could easily excite a resonance of the machine's mounting, and lead to it tipping over. You need to reduce feedrate abruptly to contstrain the following error, but a gentle resumption of feedrate would be much better.
Jon ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
