On Mon, 6 Jul 2009, Leslie Newell wrote: > Date: Mon, 06 Jul 2009 23:02:28 +0100 > From: Leslie Newell <les.new...@fastmail.co.uk> > Reply-To: "Enhanced Machine Controller (EMC)" > <emc-users@lists.sourceforge.net> > To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> > Subject: Re: [Emc-users] Servo tuning > > Thanks Jon, > > I'll study your docs. What I can't understand though is why I is > increasing the following error. >
Heres how I tune motors: One thing about "I" is its worse than useless until all the other tuning is right. To start with I would set "I" and all feed forward terms to 0 I would then adjust P first then D until have a system with good stiffness and good step response and not too much buzzing when idle. To get the best performance you will have to adjust P then D, and then repeat, inching up P and D together. Then do a long rapid move and minmize the following error _during slew_ by adjusting FF1. FF1 is needed for bare PWM amplifiers (like the 7I29) to counteract the effect of backEMF. Then do a repeated step with near maximum acceleration and adjust FF2 for minimum error during accel and deccel Once all thats done, a little bit of integral term can reduce your errors under static (or very low frequency) loads. As a variation you can adjust the feed forward terms when P and D are low, as the effects of the feedforward terms will be more pronounced. > Les > > Jon Elson wrote: >> >> Because of discontinuities is the programmed path, the I term is of >> limited usefulness. >> I usually just put a tiny amount in and leave it there. I can't give a >> fixed value, as it needs to be proportional to P. >> With P=1200, then I would expect I to be about 10. If increasing FF1 >> makes following error worse, reduce it. >> FF is not a feedback, so it will easily "overdo" the commanded velocity >> or acceleration. FF2 requires extremely small values, I often use >> something around 0.005, but you can suppress error spikes on >> acceleration very well with it. >> >> Assuming 5 TPI screws directly driven, then 1024 CYCLE/rev encoders >> produce 20480 counts/inch, which is a bit low for a system without >> velocity feedback. >> >> See my VERY well hidden article on servo tuning at >> http://wiki.linuxcnc.org/cgi-bin/emcinfo.pl?PWM_Servo_Amplifiers >> >> Jon >> >> ------------------------------------------------------------------------------ >> _______________________________________________ >> 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 > Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
