Servo Tuning Help

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23 Oct 2016 20:46 #81973 by bevins
Servo Tuning Help was created by bevins
Hi all,

I am having trouble getting my servo's tuned especially the slaved Y to A.

What I did was up the P until it stats to oscillate. Then I go back on the P until it stops oscillating. Then I have it like in the pic. But whatever I do, I cannot get the f-error to straight.



The other drives are much worse.

I tried, raising ff1, and it distorts the oscillating, but never can get it to go away.
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24 Oct 2016 02:07 #81978 by Todd Zuercher
Replied by Todd Zuercher on topic Servo Tuning Help
I'd say that is still too much P, back it off until the oscillation is minimized during the movement, as well. Then set FF1 to minimize flowing error.

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24 Oct 2016 16:00 #81991 by andypugh
Replied by andypugh on topic Servo Tuning Help
Do you have an I-Gain?

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25 Oct 2016 20:24 - 25 Oct 2016 20:38 #82057 by bevins
Replied by bevins on topic Servo Tuning Help

andypugh wrote: Do you have an I-Gain?


Yes, This is on the X and it has to be - or it goes a bit crazy.


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Last edit: 25 Oct 2016 20:38 by bevins.

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25 Oct 2016 20:27 - 25 Oct 2016 20:49 #82058 by bevins
Replied by bevins on topic Servo Tuning Help
OK, here it is with positive scale. And I fixed the div so it is more readable.


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Last edit: 25 Oct 2016 20:49 by bevins.

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25 Oct 2016 20:50 #82061 by bevins
Replied by bevins on topic Servo Tuning Help
These are KRS drives, I have removed the option of the drives handling internal pid, so it is sending out to Linuxcnc the encoder and linuxcnc is handling the PID.

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25 Oct 2016 20:53 #82062 by bevins
Replied by bevins on topic Servo Tuning Help
Here are some pics of the machine.


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27 Oct 2016 19:13 #82156 by bevins
Replied by bevins on topic Servo Tuning Help
Anyone have an at_pid config I can look at?

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27 Oct 2016 19:45 - 27 Oct 2016 19:46 #82157 by PCW
Replied by PCW on topic Servo Tuning Help
Are the drives programmed for velocity or torque mode operation?
(if torque mode, you will likely need to run a faster servo thread to get decent performance)
Last edit: 27 Oct 2016 19:46 by PCW.

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27 Oct 2016 20:36 #82158 by Todd Zuercher
Replied by Todd Zuercher on topic Servo Tuning Help
Peter, brings up a very good point. You said earlier that you disabled the drives PID. That may have been a mistake, if you disabled the drives velocity loop. Without that the drive would be operating in "torque mode" where the analog input would be a force command. This is much more difficult to tune in Linuxcnc that the usual velocity command. But to have a velocity control the drive needs to have some kind of feedback loop that needs to be tuned. You may need to study the manuals for your drives a bit more.

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