Z axis Pid tuning mesa 7i77 & Yaskawa sgda-04as

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06 Sep 2020 13:17 #180998 by Dex64
Hello
I have in my cnc mesa card 7i77 with servopacks yaskawa sgda-04as.
Now I made pid tuning for XY axis. I have a problem with Z axis. When I
have to change P value higher than 0 then axis move. I compensate it via voltage offset at drive.
Axis stops and when I move down everything is ok but when I move up then axis move by itself. Then when
I back with P value to 0 axis axis work properly in both directions (manual jogging). With P=0 ferror is huge. Do You have some advice for
me? Thank You in advance. Screen in attachments
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06 Sep 2020 13:52 #181004 by PCW
You must have some P term or you do not have position feedback
Are you sure you have the feedback in the proper direction?
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06 Sep 2020 17:32 #181045 by Dex64
Hi
Youre right. I had inverted feedback to this axis. Now it works ok. Thanks a lot.
I have one more question. How can I compensate this peak ferror in axis X and Y?
I attached screens from linux and software from driver.
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06 Sep 2020 17:37 #181047 by Dex64
Properly screens here:
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06 Sep 2020 17:38 #181048 by Dex64
From driver software :

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06 Sep 2020 17:45 #181051 by Dex64
Here from driver software:
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06 Sep 2020 18:04 #181055 by PCW
It looks to me that maybe you have the maximum velocity too high in LinuxCNC

(The PID doesn't have enough headroom to control the velocity when it gets to the slew
point of the motion, you can see the error build up until it starts to slow down again)

Normally you should not go any faster than about the velocity at 9V, so you have 10% headroom
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