On Thursday 07 May 2020 11:27:57 Jon Elson wrote: > On 05/06/2020 09:20 PM, Dan Henderson wrote: > > I’ve confirmed the fluctuation occurs when spindle-at-speed is > > configured. When I remove this feature, the spindle rpm appears to > > stabilize. It’s almost like it gets caught in a loop trying to chase > > its tail. > > This is VERY common in servo systems, and is due to delay in > response of the object being controlled. > You need to slow down the response of the PID to ignore the > delay. This may be possible by adding > D to it. > > Jon
But my msg was that a near module generated spindle.N.at-speed was never to be injected into any signal path leading back to a PID. That near's output s/b only to that input to motion, and possibly to an indicator led in the gui so the operator can be advised if its acting funkity. Flickering could be worn brushes in a brushed PMDC motor for instance. What you are describing as delays can often be fixed by the proper re-ordering of the addf's involved for the oscillating axis. That aspect of configuring LinuxCNC hasn't been mentioned recently or I wouldn't even have included that paragraph in my reply. And from Dan's description above, I think this is an entirely different critter from a timeing delay. Cheers Jon & stay well, 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) 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
