I believe this is open loop. Isn’t PID only used in closed loop control? On Thu, May 7, 2020 at 11:03 AM Gene Heskett <ghesk...@shentel.net> wrote:
> 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 > _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
