On Mon, 30 Oct 2017, Gene Heskett wrote:
Date: Mon, 30 Oct 2017 18:44:49 -0400
From: Gene Heskett <[email protected]>
Reply-To: "Enhanced Machine Controller (EMC)"
<[email protected]>
To: [email protected]
Subject: Re: [Emc-users] Spindle pid problems
On Monday 30 October 2017 15:20:35 andy pugh wrote:
On 30 October 2017 at 17:49, Gene Heskett <[email protected]> wrote:
Which is computationally less cpu usage 1, a 6 pack of mux2's, or
another pid with separate settings and just one mux2 to select which
pid gets sent to the spindle servo?
PID is not very CPU intensive, neither is mux2. I wouldn't really
worry about either.
You can see how much CPU time each module uses in HAL.
The "lincurve" component was intended specifically for this type of
situation, which is why it has outputs of the r/w style that can be
connected directly to the pre-2014 PID gain pins (which for no good
reason were bidirectional)
But in this case mux2 seems more appropriate if it is a simple switch
between states.
Between pid.sh.output and pid.sl.output. When I get everything else
working again. Probably not yet tonight as I had to come and do
something about an empty skillet for dinner.
However, I suspect that your problem is that you are trying to use P
on a controller that only really needs FF0 and I.
A dc powered spindle is a velocity servo I think, so I been trying to
follow John Thorntons wiki article from 2012 where he describes tuning a
axis servo in the velocity mode. Is this the wrong approach for a
spindle that needs to have quite stiff control?
And I just found his other description of spindle tuning, where its all
FF0 and Igain. That one however doesn't describe the hardware setup at
all, nor does it have any halscope pictures. I suspect that the spindle
John was calibrating was being driven by a vfd, which is inherently a
pretty stiff drive.
But when I get it back to where I can run it (I'm in the middle of moving
the spindle power control sequencer from the 5i25 P3 to the same on P2,
which feeds a different bob in a different box. And reconnecting it to
where I can use an A axis with those pins, and while I am up on the
ladder, I'll get the individual boxes bolted together to prevent another
short that blew a chain of 5i25's).
I really ought to build another, even bigger box, at least another 3"
deeper, and 4 or 5" taller so the A driver could fit inside it. Unforch
that would take another half a sheet of 1/8" alu plate to go with the
close to half a sheet I have on hand.
So many projects, so little 'extra' time. :)
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>
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As Andy mentioned, Spindle tuning is normally done with mostly FF0 and
then some I
Johns tutorial is for tuning a position mode loop with velocity
PID output, but your spindle is a velocity mode loop with velocity PID output
Peter Wallace
Mesa Electronics
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