Yes I'm not worried about servo following error spikes. But I'm shaking my whole machine to death. As the acceleration is instantly on. In contrast a friend's okuma can go at 40m/min without shaking. Which is amazing to watch. They are both similar size
On Thu, Jul 23, 2020, 9:42 AM Nicklas SB Karlsson < nicklas.karlsso...@gmail.com> wrote: > > hey guys > > > > I have a relatively high speed machine (3kw motors 16mm pitch ballscrews) > > 35mm linear rails, and weights 5.8 ton. I think it used to go 20m/min > > with the heidenhain control. I have been noticing a bit of jumping > around > > when doing parallel finishing 3d passed on it at high speed. and talked > to > > a couple of linuxcnc guys and found out that linuxcnc doesn't have any > jerk > > control. ... > > If I get it correct from electric motor equations it like this: Jerk could > be controlled instantly. Available jerk in direction to increase speed > decrease with speed while available jerk to decrease speed increase with > speed and this is because of induced back-emf. I assumed a given constant > magnetic flux inside motor otherwise decrease magnetic flux which may be > possible in some cases will decrease back-emf and torque and may allow > higher speed if voltage is a limitation, there is an optimal flux for best > efficiency. Even though control algorithm is different it should apply for > the common electric motors: DC, BLDC, PMSM 3-phase synchron motor, > synchronous reluctance motor and ordinary 3-phase asynchronous induction > motor. > > Not sure how good motion planner is. Read something about a PhD degree but > are not sure it was for the motion planner in Linuxcnc. > > I wrote simpler motion controller, one axis with jerk limitation and had > to spend quite much time make the corners fit perfectly at the same time it > followed the limitation and hit target. > > > at high speed high precision linuxcnc definitely needs some work at some > > stage. > > Improvements are of course always good. Maybe, but if high speed is used > then moving thru air "G0 move" or rectracting while speed is lower then > machining thru part lower precision is acceptable at higher speed. > Integrator need som time to decrease error so it might be hard work to get > both at once. > > > Regards Nicklas SB Karlsson > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
