On Sunday 05 November 2017 09:55:50 Peter C. Wallace wrote: > On Sun, 5 Nov 2017, Gene Heskett wrote: > >> 2 things. > >> > >> The recommended pid setup winds up like crazy, and takes 2 to 4 > >> seconds to respond to a change in the spindle loading that slows it > >> down. Then it over speeds and takes 10 seconds to settle back to > >> the set speed. I've tried to add some Pgain, but on a velocity to > >> velocity setup thats not working. That uses FF0 and Igain, > >> everything else is zeroed. > > First I would get FF0 set correctly (best RPM tracking with P,I,D all > zero) If this does not work at least reasonable well by itself, it > shows that you do not really have a velocity mode control (what > hardware is driving you spindle?) > > If you can get reasonable tracking with just FF0 then proceed to > adjust the I term. If it take seconds for the integral term to have an > effect, you have _way_ too small an I term, try multiplying it by 10. > You very likely will need to set the integral bound to prevent windup.
I don't believe the linuxcnc pid module has the ability to limit the wind up. And I've not played with it any more today, I finished the last bolt hole in the backing plate, then sawed out a nominally 4" square block of that 1/2" thick hard alu, wiped it down with acetone, along with the back face of the backing plates hub and superglued them together, gave it 10 minutes to get a decent grip out of the glue, then screwed the plate on the spindle backwards, turned the od to match the hub, and a 15 line program is now very slowly gnawing out a 69.2mm hole in the center, which should be a press fit on the spindles thrust flange that the hub normally pulls up to. It will get, while the glue still holds it, a couple of 4mm bolts about an inch apart, and a draw bolt drilled tangentally to the center of its cross section diametrically opposite the 4mm bolts. Once that done, my collet ejector will knock it loose from the glue, everything cleaned up and the 4mm bolts installed, and a 1/8th inch cut thru the middle of the drawbolt. Then when the plate is installed face forward, the draw bolt will get an ain't never gonna slip grip on the spindle flange. Instant locked to the spindle chuck that shouldn't unscrew itself with a vfd and 1 hp motor wanting to reverse it as fast as it can. Makes the dual drive belts scream for mercy with the smaller 3 jaw mounted. Then I'll play with FF0 for min "cruising error", on the G0704 then some I for better control with variable loads. Someone said 1 khz servo thread was too fast, because there weren't enough counts in a single cycle, and I think that idea has some merit, but what I really need is a lot more slots in my encoder, but stability went out for lunch the last time I tried that slower thread. > Note the using FF0 and I alone should work for a velocity mode drive. > if you have closer to a torque mode drive, the tuning will be > different Stiff as a board speed regulation is what I want. I want it to feed full power to the motor 5ms after it hits the start of a heavy cut that slows it 10% in that same 5ms. Full power in this case is 15 amps at 127 volts dc, (its a 90 volt, 9.7 amp motor) where it will run free at the requested speed on about an amp. The encoder however is only 278 edges per turn. You can only put so many slots with a .028" diameter tool in a disk thats not quite 2.5" OD. There's not a heck of a lot of room under that green cover on a G0704. Thank you Peter. I'll certainly try lots more Igain. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
