On Thursday 17 May 2018 10:40:59 Maxime Lemonnier wrote:
> Hi Gene,
>
> My use case has nothing to do with machining. I'm using a cnc mill as
> a precise robot. For the benefit of an eventual future user with the
> same use case, imagine you have a camera with a signal that triggers
> at the begining of each capture, and that you're capturing during CNC
> motion. suppose you want to the the PRECISE moment when the capture
> started. Well se my previous message and use that code:
>
> net name0 ppmc.0.encoder.03.position mirror.0.actual #I acutaly used
> linksp Apos-fb => mirror.0.actual
> net name2 ppmc.0.encoder.07.position mirror.0.mirror
> net name1 ppmc.0.encoder.07.index mirror.0.index
> net name3 ppmc.0.encoder.07.index-enable mirror.0.enable
>
> -------------------
> component mirror "index-enable hack";
> pin in bit index;
> pin in float actual;
> pin in float mirror;
> pin io bit enable;
> pin out float result;
>
> function_;
> license "GPL"; // indicates GPL v2 or later
> ;;
>
> if(index == 1)
> {
> result = actual - mirror;
> enable = 1;
> }
>
> you will obtain
>
>
>
> the little plateaux in mirror.0.result are the position at which frame
> started.
The idea I assume is to capture a few video frames of the pickup so you
can analyze any errors in the pickup motion on a frame by frame basis.
Or maybe find out why this instance was a miss-pick. Neat thinking.
Interesting, thank you for sharing.
> On Thu, May 17, 2018 at 10:24 AM, Gene Heskett <ghesk...@shentel.net>
wrote:
> > On Thursday 17 May 2018 08:34:27 Maxime Lemonnier wrote:
> > > Hi all,
> > >
> > > I'm trying to implement a somewhat exotic behavior with EMC2. I
> > > have a servo setup with two Pico Systems univpwm boards. I have
> > > spare encoder channels I want to use to precisely checkpoint the
> > > position of a channel when an external signal is triggered. So I
> > > have, concretely, encoder.03's A and B wires connected to two
> > > different univpwm channels (channels 3 and 7, so in HAL,
> > > ppmc.0.encoder.03 and ppmc.encoder.07).
> > >
> > > encoder.03's Z wire is connected to channel 3 BUT NOT to channel
> > > 7. My trigger is connected to channel 7's Z.
> > >
> > > I would like to configure HAL to simply zero-out channel 7 when it
> > > receives the trigger pulse, then I would write a comp that output
> > > the position at which the trigger was pulsed using the delta
> > > between encoder 3 and 7.
> > >
> > > How could I achieve that?
> > >
> > > Thank you very much.
> >
> > Not exactly a solution, but from the man 9 encoder page,
> > encoder.N.reset bit in
> > When true, counts and position are reset to zero immediately.
> >
> > but you are zeroing the encoder generating the z pulse. And I don't
> > grok the reason. I could see useing 3's z to zero the #7 encoder for
> > some purpose on a dual motor gantry axis, but since I don't have one
> > of those critters, its not something I've needed to do. Perhaps you
> > could expand on what the result should be?
> >
> > A pair of mux2's used as sample-holds, feeding a sum2 with one
> > inputs scale setp'd to -1, will give you a diff between the
> > encoders, but not knowing the reason, the control of the mux2.sel's
> > will be up to you to 'net' up in your .hal files.
> >
> > Because there is intertia in the mechanicals slowing the turn-around
> > time at the bottom of a g33.1 rigid tap, something I usually do by
> > wrapping it in a peck cycle because the G0704's draw bolt is such a
> > puny thing I can't grab a tap by the shank and stop the slippage, I
> > am useing 2 mux2's as sample-hold's, feeding the sum2 with one
> > inputs scale set to -1.000000, each mux2's active input feed from
> > encoder.0.position, but one mux2.sel is tied to motion's reverse
> > signal freezing it when motion issues the spindle-reverse command,
> > and the 2nd mux2.sel is watching encoder.0.velocity to detect that
> > the spindle has actually moved one count in reverse. The sum2 output
> > is then the difference in counts. With a one count diff as the error
> > budget. Thats 1.5 degrees of spindle rotation on the Sheldon but a
> > very small fraction of a degree on the G0704 due to the location of
> > the encoders a/b signals. There's more of course so the axis display
> > is stable but thats the gist of it.
> >
> > Without knowing more, I can't suggest more.
> >
> > --
> > 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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--
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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