Servo Tuning Advice

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01 Nov 2012 18:12 #26180 by Todd Zuercher
Replied by Todd Zuercher on topic Servo Tuning Advice
This is a wood working machine, so normal cutting feed speeds are a lot higher. Since this is going to mostly do 2.5-D Carving and engraving I am hoping that it won't matter to much.

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01 Nov 2012 23:08 #26187 by Todd Zuercher
Replied by Todd Zuercher on topic Servo Tuning Advice
Might there be any advantage to messing with the Traj period? My hal and ini files do not currently have any reference to it.

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02 Jan 2013 01:25 #28269 by mhaberler
Replied by mhaberler on topic Servo Tuning Advice
I made a stab to fix this error, please see here:

git.mah.priv.at/gitweb/emc2-dev.git/comm...276efd65f62684b77f57 :

motion: introduce motion.ferror-mode

by default (motion.ferror-mode == 0), ferror is computed based on the last commanded position, which is problematic with velocity-mode drives
if motion.ferror-mode == 1, ferror is calculated based on the new commanded position, and following error checks are postponed until after the new commanded position is calculated.

based on v2.5_branch . this is untested on a real machine.

please let me know if this makes a difference if you

setp motion.ferror-mode 1

- Michael

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02 Jan 2013 17:42 #28297 by mhaberler
Replied by mhaberler on topic Servo Tuning Advice
further to the aforementioned patch, here are two halscope shots taken off a stepper servo config - there is some indication that the patch does what we want:

scoping axis.0.error and pid.0.error

motion.ferror-mode set to 0:
static.mah.priv.at/public/motion-ferror-mode-0.jpg

note wildly diverging shapes

motion.ferror-mode set to 1:
static.mah.priv.at/public/motion-ferror-mode-1.jpg

pretty commensurate

- Michael

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02 Jan 2013 21:14 #28303 by Todd Zuercher
Replied by Todd Zuercher on topic Servo Tuning Advice
Could I get some brief instructions how to apply the patch?

I can't say for sure if I will test it, as the machine in question has been working acceptibly for a month or two, and I have s back log of work I need to catch up on.

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02 Jan 2013 21:30 #28305 by mhaberler
Replied by mhaberler on topic Servo Tuning Advice
I'll push this through the buildbot so we should have a package to test shortly

are you running 2.5 or master?

- Michael

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02 Jan 2013 23:05 #28312 by Todd Zuercher
Replied by Todd Zuercher on topic Servo Tuning Advice
I'm running 2.5

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03 Jan 2013 00:06 #28318 by mhaberler
Replied by mhaberler on topic Servo Tuning Advice
the ferror-mode 2.5-based RIP package is now online: buildbot.linuxcnc.org/dists/lucid/scratc...binary-i386/?C=M;O=D

I think it's this one: buildbot.linuxcnc.org/dists/lucid/scratc...ode~dafe9ea_i386.deb

- Michael

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10 Jan 2013 21:38 #28547 by mhaberler
Replied by mhaberler on topic Servo Tuning Advice
the ferror-mode patch has been merged into v2.5_branch.

- Michael
The following user(s) said Thank You: Todd Zuercher

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10 Jan 2013 22:23 #28549 by Todd Zuercher
Replied by Todd Zuercher on topic Servo Tuning Advice
Now hopefuly someday I will find the time to try it out. It won't happen in the near future.

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