PID tuning the THC

More
30 Jul 2020 01:10 #176436 by snowgoer540
Is there anyone who took the time to PID tune the THC, or does everyone just leave it at the default settings? I ask because I was talking with Cody about how his THC is slow and lags behind, and at times in the past I've noticed that it seems like mine doesn't keep up as well. Despite the fact that my Z axis is capable of 400+ Dinosaurs per minute. He was asking how to speed it up, and since I wasn't completely sure, he resolved to messing with the P value (upwards of 50) to get it to follow appropriately.

At any rate, I am not sure if that is the correct approach or, maybe it's best to ask what the recommended approach is? I know in my research for PID tuning a spindle, it gets complicated, and one recommendation was to set the P value as high as possible until it oscillates, drop it down. and then adding in I and D to fine tune it. Seems much more difficult for the THC.

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

More
30 Jul 2020 02:13 #176449 by phillc54
Replied by phillc54 on topic PID tuning the THC
I have mine at 10 and seems ok for what I do. It does seem to vary a bit between machine, acceleration and velocity would play a part. I think that just adjusting the P would in most cases be sufficient, depending on how particular you are.
The following user(s) said Thank You: snowgoer540

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

More
30 Jul 2020 03:48 #176457 by rodw
Replied by rodw on topic PID tuning the THC
If the chief test pilot and keeper of the dinosaurs wishes to play with PID tuning, I would recommend that he installs SIM_PIN in his ini file
linuxcnc.org/docs/2.8/html/man/man1/sim_pin.1.html

And configure it so he can modify the THC PID parameters while cutting. That way you don't have to waste time editing settings between runs.Then you need to spend some quality monitoring arc voltage in halscope. I'm not sure if Plasmac has one but it is also good to measure the error (difference between desired volts and actual volts at a higher scale). Also plot the thc enable signal so you know when pid control starts. There are a number of articles on the net that talk about PID tuning. The Wiki has some good diagrams
en.wikipedia.org/wiki/PID_controller.

I've only ever used the plasmac defaults but have earnt my credentials in THC pid tuning pre-plasmac...

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

More
30 Jul 2020 11:07 #176492 by snowgoer540
Replied by snowgoer540 on topic PID tuning the THC

If the chief test pilot and keeper of the dinosaurs wishes to play with PID tuning, I would recommend that he installs SIM_PIN in his ini file
linuxcnc.org/docs/2.8/html/man/man1/sim_pin.1.html


There's so many things to know about LinuxCNC. It must take years to get your head fully wrapped around everything. And then on top of that, remember all the things you learned in the years previous :laugh:. Well, I guess I learned two things today (Phill implied you can link and unlink pins in Halshow).


And configure it so he can modify the THC PID parameters while cutting. That way you don't have to waste time editing settings between runs.Then you need to spend some quality monitoring arc voltage in halscope. I'm not sure if Plasmac has one but it is also good to measure the error (difference between desired volts and actual volts at a higher scale). Also plot the thc enable signal so you know when pid control starts. There are a number of articles on the net that talk about PID tuning. The Wiki has some good diagrams
en.wikipedia.org/wiki/PID_controller.

In addition, maybe he can move the ball further down the field on his project to add PID control to his Tormach spindle. I got left hanging a bit over in the Pathpilot thread. In fairness, maybe I was asking too many questions at once.

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

More
30 Jul 2020 12:40 - 30 Jul 2020 12:40 #176498 by bevins
Replied by bevins on topic PID tuning the THC

If the chief test pilot and keeper of the dinosaurs wishes to play with PID tuning, I would recommend that he installs SIM_PIN in his ini file
linuxcnc.org/docs/2.8/html/man/man1/sim_pin.1.html


lol, WTF is that? You keep dragging this stuff up I never heard of. Did you write the docs? lol

SIM_PIN.... lol
Last edit: 30 Jul 2020 12:40 by bevins.
The following user(s) said Thank You: snowgoer540

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

More
30 Jul 2020 13:08 #176504 by snowgoer540
Replied by snowgoer540 on topic PID tuning the THC

If the chief test pilot and keeper of the dinosaurs wishes to play with PID tuning, I would recommend that he installs SIM_PIN in his ini file
linuxcnc.org/docs/2.8/html/man/man1/sim_pin.1.html


lol, WTF is that? You keep dragging this stuff up I never heard of. Did you write the docs? lol

SIM_PIN.... lol


I'm always under the impression that I'm super out of the loop/behind the curve with this stuff. Good to know I'm not alone anyways lol.

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

More
31 Jul 2020 07:22 #176607 by rodw
Replied by rodw on topic PID tuning the THC

If the chief test pilot and keeper of the dinosaurs wishes to play with PID tuning, I would recommend that he installs SIM_PIN in his ini file
linuxcnc.org/docs/2.8/html/man/man1/sim_pin.1.html


lol, WTF is that? You keep dragging this stuff up I never heard of. Did you write the docs? lol

SIM_PIN.... lol


Dewey Garrett made me do it! The original External offset branch he wrote had some SIM_PIN windows that we used to tune the THC PID. It was pretty handy. LIke you I had never heard of it either. I think Bevins the chief router pilot might be able to use it to tune his servos perhaps.

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

Moderators: phillc54
Time to create page: 0.085 seconds
Powered by Kunena Forum