On 9/19/23 20:12, Peter Wallace wrote:
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)
No PID in this axis, it is a closed loop stepper/servo, PID is in
controller and linuxcnc has no access to the encoder in the motor.
I am already using 4 of these motors in other machines, they get where
you send them, if they can't get there they'll close an alarm contact
and linuxcnc is e-stopped in the next millisecond. they do have an
error, but that error also controls the motor current, so unless really
working hard, very little heat. At normal working speed so quiet that
you swear Casper the Ghost was turning the cranks.
So how do you hookup the feedback when there isn't any? The man page
says the frequency is in hertz or is that a typu and its nanoseconds?.
From the manpage:
siggen.N.frequency float in
The output frequency for signal generator N, in Hertz.
The default value is 1.0 Hertz.
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/>
_______________________________________________
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users
