On Thursday 17 September 2015 10:44:07 Gene Heskett wrote: > Thanks for the link Andy, thats very helpful. I'll have to play with > a calculator of course, some of which you see above, but now I have a > clue as to what the heck i am doing rather than blindly trying numbers > for effect. > > Cheers, Gene Heskett
I wound up with stuff in the ballpark of what I wrote, a 5 rpm difference at zero speed, and scaled up by 1.1 as the speeds rise. But I have a secondary problem still, With a limit3 with a maxa setting in front of the pid.s.command, no matter what I do with the maxa setting, which does control the speed it responds to an m3-m4-m3 transition, it always overshoots to about 1.4x the set speed as it winds up in the new direction, even if I set maxa so low it takes a very leasurely 10 seconds to turn it around. The overshoot appears to be the same magnitude regardless of the speed of the turnaround. But it seems to me that at a speed change rate of accel slow enough the pid has total control, there should not be any overshoot, but something sure seems to be getting wound up & has to be unwound before it settles. Does this ring any bells? Increased Dgain seems to help, but also seems to make the whole thing sing at about the 1KHz servo-thread frequency. Thanks for any clues, or links to PID tuning tuts more detailed than the single paragraph in the new 2.7 document pdf. This is not a position servo, but a velocity, and most tuts I can google seem to position mode. 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> ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
