> 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
