On Tuesday, May 08, 2012 05:34:22 PM Peter C. Wallace did opine:
> On Tue, 8 May 2012, gene heskett wrote:
> > Date: Tue, 8 May 2012 16:52:37 -0400
> > From: gene heskett <ghesk...@wdtv.com>
> > Reply-To: "Enhanced Machine Controller (EMC)"
> >
> > <emc-users@lists.sourceforge.net>
> >
> > To: emc-users@lists.sourceforge.net
> > Subject: Re: [Emc-users] PID controller Q's
> >
> > On Tuesday, May 08, 2012 04:42:52 PM andy pugh did opine:
> >
> > On 8 May 2012 21:06, Dave <e...@dc9.tzo.com> wrote:
> > > You have no Pgain, but Igain and Dgain. That's a problem. An all I
> > > and D loop is almost always unstable.
> >
> > That depends….
> >
> > For a spindle P gain is not much help, as you need a non-zero PID
> > output even when at the set speed (and when the error is zero). That
> > is why the Wiki example is all-I.
> >
> >The page I am looking at right now says D-I are both 1.0.
> >
> >Silly Q probably, but could the pid.0.command value also be sent to
> >sum2.0.in0, and the pid.0.output sent to sum2.0.in1 to furnish the
> >desired offset, allowing the pid module to work with a much more
> >balanced (read closer to zero) output? To my simple mind, which
> >ignores the latency of a 1 khz servo thread for all this, that does
> >seem like it should be a workable scenario. Let sum2.0.output drive
> >the pwmgen.0.value.
>
> uneccesary as this is exactly what FF0 does
>
From the pid man page:
pid.N.FF0 float rw
Zero order feed-forward term. Produces a contribution to the
output that is FF0 multiplied by the commanded value. For position
loops, it should usually be left at zero. For velocity loops, FF0 can
compensate for friction or motor counter-EMF and may permit better tuning
if used properly.
Multiplied. That sound like I'd need a gain reduction term, or is that one
of the other Ngains?
Thanks Peter. The wife is back from the dentist so we better go vote &
find some dinner. Later everybody.
> Peter Wallace
> Mesa Electronics
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>
Truth never comes into the world but like a bastard, to the ignominy
of him that brought her birth.
-- Milton
------------------------------------------------------------------------------
Live Security Virtual Conference
Exclusive live event will cover all the ways today's security and
threat landscape has changed and how IT managers can respond. Discussions
will include endpoint security, mobile security and the latest in malware
threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/
_______________________________________________
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users
