2009/10/22 Jon Elson <[email protected]>: > Good hypothesis and data taking! So, it seems the problem is the > encoder counter sees > a zero velocity between actual encoder counts, and tells the slaved axis > to stop NOW! Then a > count comes in, and it says MOVE NOW! Yes, I can see this is a definite > problem.
I am not sure that this is the full story anyway. The oscillations are typically nothing like encoder frequency (say 200Hz) but nearer 5 Hz. Also note that G33 et-al are position-mode not velocity-mode. The simple solution might be for stepconf to always connect to position-interpolated rather than just position. With a good encoder this seems to work fine in most cases as long as the axis accelleration is adequate. There might be an argument for using a more sophisticated PID type controller, but the correct P. I and D would almost certainly be strong functions of spindle speed. Add to that the complication that you are trying to control to position but are limited by velocity and acceleration and it becomes difficult to think about, let alone work out how it should be coded. An alternative might be to keep things much as they are, but to have a parameter in the G-code for how much "run up" it has. It then becomes a somewhat simpler trajectory planner issue to get to the thread start at the right speed next time the index comes round on the unloaded spindle and only then to enter the current position-feedback mode to stay on-pitch and allow for spindle velocity changes. I think that might actually be the essence of how Chris' patch works, though that just waits to get a better spindle speed estimate I think. -- atp ------------------------------------------------------------------------------ Come build with us! The BlackBerry(R) Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9 - 12, 2009. Register now! http://p.sf.net/sfu/devconference _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
