On Wednesday, February 2, 2022 1:57:33 PM EST Peter C. Wallace wrote: > On Wed, 2 Feb 2022, Thaddeus Waldner wrote: > > Date: Wed, 2 Feb 2022 01:39:29 -0600 > > From: Thaddeus Waldner <thadw...@gmail.com> > > Reply-To: "Enhanced Machine Controller (EMC)" > > > > <emc-users@lists.sourceforge.net> > > > > To: Enhanced Machine Controller <emc-users@lists.sourceforge.net> > > Subject: [Emc-users] Stepper PID > > > > ��Hi, > > > >I have a pi4 running the 2.8.2 iso. I have it connected to a Mesa 7i96 > >and from there I��m driving small stepper motors with tmc2209 > >��stepstick�� drivers. I think my step rate at max speed is around > >8khz > > > >I get around +-70us? Max latency. > > > >I��ve been having an issue with what I think is latency which makes > >the steppers sound like they have bad bearings. Raising the servo > >period to 2ms made it worse. So I tried a faster servo thread and > >discovered the issue pretty much goes away with the servo period at > >250us. At that rate I start running into joint following issues. 5A I > >then learned that with the servo period at 1ms, if I lower the > >stepper PID P parameter to 100 instead of the 1000 set by the > >configuration wizard, the noise goes away completely and the steppers > >run buttery smooth. > > > >I have a few questions: > >1) what are the implications of running the PID stepper with p=100? > > Worse following error > > > 2>) why is servo thread jitter even making into the stepper pulse train > with a > >Mesa Ethernet card and no communication errors? Do I have anything > >misconfigured? > > The problem is that the PID loop makes bogus velocity corrections > because of position sample time jitter (which may be as high as a few > hunderd usec on RPI4 Ethernet) > > > I suspect that you are not using the DPLL, or that it is not setup > properly. For a RPI4 I would suggest these settings: > > > setp hm2_7i76e.0.dpll.01.timer-us -200
With no previous guidance, I set my 7i90 with SPI interface at -50 u- secs, should I raise that? > set hm2_7i76e.0.stepgen.timer-number 1 > > These should reduce the stepgenb position sampling jitter to a > fraction of 1 usec. > > >Thanks > > Peter Wallace > Mesa Electronics Thanks, stay well Peter. 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, 1940) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis 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
