On Sunday 09 December 2012 20:19:59 andy pugh did opine: > On 10 December 2012 00:40, Gene Heskett <[email protected]> wrote: > > I can't make Pgain cause more than about a 10% of that range cyclic > > wibble, not near enough to hear it with the spindle at say 6 rps > > commanded. At least at Pgains up to 150 or so, with FF0 = 100, FF1 = > > 20 and FF2 = 10. > > What makes you think that you need FF1 and FF2? This s your spindle > that we are talking about here, I think? > Yes. In my playing this afternoon, it seemed to have the effect of speeding up the corrections when I loaded it, or when I changed the speed from axis. It seems much 'stiffer' with the higher order FF's applied.
> > Should I be able to induce a rail to rail oscillation with Pgain? > > Not always. In the case of your spindle I think the physical > time-constant and the servo period might be so far apart that it might > never happen. > > > pid.N.feedback-deriv float in > > > > I hadn't noticed this before, so encoder.0.velocity only feeds the > > > > pid.N.feedback pin. > > > > It sounds as if I should feed both pins with encoder.0.velocity. > > Done, but not tested yet. > > Not in your case, as encoder velocity is the controlled quantity, not > the derivative thereof. > > encoder.velocity is only an appropriate feedback-deriv term in a > position loop. But this is not a position loop per sei, its a velocity loop, working in the rps domain. Does that not change things, and if not, why? Thanks Andy. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> is up! Art is anything you can get away with. -- Marshall McLuhan. I was taught to respect my elders, but its getting harder and harder to find any... ------------------------------------------------------------------------------ LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial Remotely access PCs and mobile devices and provide instant support Improve your efficiency, and focus on delivering more value-add services Discover what IT Professionals Know. Rescue delivers http://p.sf.net/sfu/logmein_12329d2d _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
