On Tue, 19 Sep 2023, gene heskett wrote:
Date: Tue, 19 Sep 2023 19:23:23 -0400
From: gene heskett <ghesk...@shentel.net>
Reply-To: "Enhanced Machine Controller (EMC)"
<emc-users@lists.sourceforge.net>
To: "'Enhanced Machine Controller (EMC)'" <emc-users@lists.sourceforge.net>
Subject: [Emc-users] question for Peter C. Wallace
Greeting Peter;
I hope this finds you well.
I am installing a new A axis on my go704, and am trying to exercise it before
moving 99% of the actual driver code code in from another machine with
identical hdwe for its B axis.
I have loaded a siggen to use its triangular drive as input to the
joint.03.position-cmd, with the amplitude set to 2.5 and this for the rest of
the dummy code:
setp hm2_5i25.0.stepgen.03.enable true #turn it on
setp siggen.0.frequency 10
setp siggen.0.amplitude 2.5
setp hm2_5i25.0.stepgen.03.steplen 4000
setp hm2_5i25.0.stepgen.03.stepspace 10000
setp hm2_5i25.0.stepgen.03.dirhold 6000
setp hm2_5i25.0.stepgen.03.dirsetup 6000
net mtr-test
<= siggen.0.triangle =>
hm2_5i25.0.stepgen.03.position-cmd
So tb2-20 to 23 on the 7i76D is supposed to be stepgen.03.outputs.
man siggen says it should be symmetrical if no offset is set. But dir on
neither pin is anywhere near 50/50, closer to 5/95, and faster than the above
10 a sec by quite a bit, and the step terminals are a solid 5 volt or zero
volts, no activity at all.
This on a 4 channel storage scope with a 350MHz bandwidth. Siglent's best.
That puppy doesn't miss a thing.
Did I miss a setp above?
Thanks Peter.
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, 1940)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/>
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You would also need to set reasonable stepgen acceleration and
velocity limits.
In addition, It may be that because you have a non-differentiable
position command (Triangle wave) that you have started an
instability in the built in position mode, so a sine wave would
be a better test.
For best performance where the are possible large following
errors it's better to use the stepgens in velocity mode and
close the (local) position with a PID loop.
Typical settings for the loop are
P = 1/servo period so 1000 for a 1 ms servo thread
FF1 = 1.000
FF2 = Time between Position read and velocity write
(say 20 us on a PCI card =.00002, perhaps 200 usec on a
Ethernet card = .0002)
Peter Wallace
Mesa Electronics
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