Voltage divider for Mesa THCAD-10?

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29 Oct 2024 01:27 #313398 by PCW
Can you post your hal/ini files?
 

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29 Oct 2024 01:33 #313399 by tommylight
Thank you for clearing that up, although should have been at the very first post. :)
Your servo period set at 25597 was what sent me in that direction, that should not be edited normally.

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29 Oct 2024 01:57 #313400 by mal136
Yes of course thank you so much for your help!

see attached 

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29 Oct 2024 02:06 #313401 by PCW
The main hal file: plasma_v2.hal
has not been attached.

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29 Oct 2024 02:33 #313403 by mal136
Hmm that's odd ; I uploaded it but it seems it didn't load or attached, apologizes hopefully this time it works .
Attachments:

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29 Oct 2024 02:38 #313404 by PCW
OK the reason for the stepgen instability is the the P terms are all set to 10000
but should be 1000 for a 1 ms servo thread.

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31 Oct 2024 01:26 #313517 by mal136
Great news! It works now!, that P value was definitely the issue. I set my P value to 1000 as advised and the machine operate perfectly now!,

Is the P value something i calculate based on my jitter servo value or is that just a fixed value of 1000? 

For example, if my servo thread jitter reads 15586, would that mean my P term should be 15.586? (15586 divided by 1000?) 


I appreciate all you guys help so much , you are amazing and i apologize for being a noob. I'm doing my best to learn and im getting better everyday, thank you all so much!

Now i have to get a few things polished up and tune it all in. I am so excited!!

I'd love to know why the PNFconfig generates that as the P value? All the DIY's i followed never mentioned that P value was something i had to modify/tune.

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31 Oct 2024 01:40 #313518 by PCW
Pncconf initially sets the P value for stepgens to 1/servo_period in seconds
(so 1000 for a 1 ms servo thread)

The physical meaning of this is that any position error (due to differences
between LinuxCNCs and the FPGA card clock, jitter, and the time
between reading the stepgen position and updating the velocity register)
is corrected by the next thread invocation.

A P value higher than 1/servo_period will overcorrect, and a a value higher
than 2/servo_period will result in oscillations.



 
The following user(s) said Thank You: mal136

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31 Oct 2024 01:45 #313519 by tommylight
P value for stepper systems should never be changed, and it depends only on servo period timing, so for a servo period of 1000000 (1 million) it always should be 1000.
Servo period should also never be changed, except in some situations, like when using torque mode servo systems that benefit from faster iteration, or when using a PC with very bad latency. And whenever servo period is changed, so should the PID values.
The math there is 1/servo period in nano seconds, so for
1000000 servo period = 1000 P value
500000 servo period = 2000 P value
2000000 servo period = 500 P value
That is all for steppers in position mode, for servos and steppers with encoder feedback to LinuxCNC those values must be tuned.

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