NOT SITTING AT ABSOLUTE POSITION AFTER UPGRADE FROM 2.7 to 2.8
- andypugh
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13 Nov 2018 16:41 #120572
by andypugh
Replied by andypugh on topic NOT SITTING AT ABSOLUTE POSITION AFTER UPGRADE FROM 2.7 to 2.8
It is not impossible that the conversion script made a mistake (I wrote that script, so the chances are not low)
The old configs should be backed-up in a folder called (machine_name).old in the config folder.
It might be worth checking that the PID terms haven't changed. Check both that the values are the same in the new and old INI, and that the HAL file passes the same values to the pid component.
I think there might be something not quite right with derivative error calculations at the moment ( github.com/LinuxCNC/linuxcnc/issues/466 ) but that should not have any effect on steady-state behaviour.
Updating should not require that PID be re-tuned, except possibly if the servo thread rate was changed. Is that still the same?
The old configs should be backed-up in a folder called (machine_name).old in the config folder.
It might be worth checking that the PID terms haven't changed. Check both that the values are the same in the new and old INI, and that the HAL file passes the same values to the pid component.
I think there might be something not quite right with derivative error calculations at the moment ( github.com/LinuxCNC/linuxcnc/issues/466 ) but that should not have any effect on steady-state behaviour.
Updating should not require that PID be re-tuned, except possibly if the servo thread rate was changed. Is that still the same?
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- PCW
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13 Nov 2018 16:42 - 13 Nov 2018 16:43 #120573
by PCW
Replied by PCW on topic NOT SITTING AT ABSOLUTE POSITION AFTER UPGRADE FROM 2.7 to 2.8
15 or so mV of offset is possible with contributions from the drive and the 7I77
and this would account for the position error with a P term of 50
(this may also change a bit depending on temperature)
I would probably just add a bit of I term as Andy suggested to fix small static offsets.
Another option is to tweak the offset via the PID components bias pin
AFAIK the only recent change in the PID component is that the FF1 calculation
now detects if the command-deriv pin is connected (it had a bug and did not detect this before)
This would have no effect and static positions so its not related to the offset issue.
and this would account for the position error with a P term of 50
(this may also change a bit depending on temperature)
I would probably just add a bit of I term as Andy suggested to fix small static offsets.
Another option is to tweak the offset via the PID components bias pin
AFAIK the only recent change in the PID component is that the FF1 calculation
now detects if the command-deriv pin is connected (it had a bug and did not detect this before)
This would have no effect and static positions so its not related to the offset issue.
Last edit: 13 Nov 2018 16:43 by PCW.
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13 Nov 2018 16:50 #120574
by andypugh
The entire config folder (2.7 version) should have been automatically backed-up into the (machine-name).old folder.
Replied by andypugh on topic NOT SITTING AT ABSOLUTE POSITION AFTER UPGRADE FROM 2.7 to 2.8
What is the process for getting my config back to 2.7 compatible?
The entire config folder (2.7 version) should have been automatically backed-up into the (machine-name).old folder.
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- COlger81
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13 Nov 2018 16:58 #120578
by COlger81
Replied by COlger81 on topic NOT SITTING AT ABSOLUTE POSITION AFTER UPGRADE FROM 2.7 to 2.8
It did make a backup but it looks to be in Master (joints) format.
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13 Nov 2018 17:43 #120583
by andypugh
Replied by andypugh on topic NOT SITTING AT ABSOLUTE POSITION AFTER UPGRADE FROM 2.7 to 2.8
Is there an old.old directory?
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13 Nov 2018 18:17 #120588
by COlger81
Replied by COlger81 on topic NOT SITTING AT ABSOLUTE POSITION AFTER UPGRADE FROM 2.7 to 2.8
Yes, the file 2 posts up is from the .old directory.
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13 Nov 2018 18:19 #120589
by COlger81
Replied by COlger81 on topic NOT SITTING AT ABSOLUTE POSITION AFTER UPGRADE FROM 2.7 to 2.8
SOLVED:
I was able to adjust the balance on the drive. Not sure what caused the shift in voltage though..
I was able to adjust the balance on the drive. Not sure what caused the shift in voltage though..
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13 Nov 2018 19:02 #120594
by COlger81
Replied by COlger81 on topic NOT SITTING AT ABSOLUTE POSITION AFTER UPGRADE FROM 2.7 to 2.8
Thanks for the help guys. I'm also trying to find the floating pin that displays following errors.
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14 Nov 2018 12:39 #120665
by andypugh
Replied by andypugh on topic NOT SITTING AT ABSOLUTE POSITION AFTER UPGRADE FROM 2.7 to 2.8
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