Mesa 7i97T & LinuxCNC setup struggles

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1 year 4 months ago #329898 by BlownCorona
Yesterday evening i was using chatgpt to help understand some of the nuts and bolts of what certain values mean. i made progress but perhaps you can check its homework.

i did set the following errors wider which has prevented this error occurring for the most part, though i understand this should eventually be taken right back down to the tight window it should be.
FERROR = 10
MIN_FERROR = 5

notably, it suggested changing the PWM scale from 10 to 1, claming that this would provide the expected +-10V and the voltage limits coming from the max outputs which on the surface makes sense and got me to the point where i was tuning a motor that was either violently oscillating or buzzing angrily, tuning pid values to a very low point gave a quieter (but not silent) motor but it was sluggish.

Now it could be that im not in a position to tune properly, or i could have screwed the code up much worse because i am quite aware that chatgpt is not our savior and it will be confidently wrong.

the documentation here supports the claim that the scale should = 1 however im not certain why mesaCT set that scale as = 10

www.linuxcnc.org/docs/html/man/man9/pwmgen.9.html

feels like progress, and i dont think im far off cracking it.

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1 year 4 months ago #329909 by PCW
Changing the PWM scale changes the scaling of all PID parameters.
That is, a P term of 10 with a PWM scale of 10 is the same as a P term
of 1 with a PWM scale of 1, In both cases an error of 1 mm generates a
full scale (+ or - 10V)

There is no reason on a torque mode drive to change the default 
PWM scale of 10 (a scale of 10 means the PID output is scale in volts)
 
The following user(s) said Thank You: tommylight

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1 year 4 months ago #329926 by BlownCorona
ok that makes sense, and after spending some more time working on it, including taking the scale back to 10, i have it now in a pretty good spot where i would consider it time to start tuning.

does the halscope guide tommy put together also work for tuning torque mode PIDs? otherwise im currently hunting out an equally well put together guide so i dont resort to just changing numbers and seeing what happens.

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1 year 4 months ago #329927 by PCW
I would try the steps A,B,C of example 1 I posted earlier

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