Stepper configs have suboptimal P term setting

More
9 years 10 months ago #83920 by guymalpass
Hi Peter,
I'm running a closed loop stepper system using a 7i76, 7i77 and 5i25 and have recently noticed your post about P terms being 1/servo period. I have been using a P term of 170 so decided to try out 1000 (my servo period is 1000000) but I just get oscillation. Is there anything I should be looking at to explain why I am so far off your recommended value?
To clarify my stable settings are P-170 I-0 D-0 FF1-0.994 FF2-0.000025 on master branch.
Thanks,
Guy

Please Log in or Create an account to join the conversation.

More
9 years 10 months ago #83921 by PCW
For a closed loop system (closed with encoder feedback)
1/T-servo is probably way too much P gain
because of delays from step output to physical motion

Only very tiny delays are present for "local" pid feedback so the 1/T-servo works and matches
the drivers position mode settings (that correct the position error completely in the next servo period)

Please Log in or Create an account to join the conversation.

More
9 years 10 months ago #83922 by guymalpass
My mistake I thought the post was referring to closed loop setups.
Thanks

Please Log in or Create an account to join the conversation.

More
9 years 10 months ago #83923 by PCW
NP, I probably was not clear, its a bit confusing since they are both closed loop
(though one is closed locally to the stepgen position counter)

Please Log in or Create an account to join the conversation.

Moderators: cmorley
Time to create page: 0.170 seconds
Powered by Kunena Forum