If you feed those averages to the PID controller, that PID is reacting to old data and you get either very sluggish control or oscillation.
The best way is to predict the future and the have the control programmed to make that predicted future the future you want. That hockey quote comes to mind, "I don't skate to the puck, I skate to where the puck will be." PID algorithms using averaged data are even worse and "skate to where the puck used to be." A PLL is actually a predictive model of the spindle that tells you where the index will be at any point in time, past or future. It works in as much as spindles don't teleport randomly to different angles and RPMs but exhibit predictable behavior. For very short periods of time, (one servo cycle) the prediction is very good. On Wed, Jul 21, 2021 at 12:18 PM Gene Heskett <ghesk...@shentel.net> wrote: > On Wednesday 21 July 2021 14:46:26 Chris Albertson wrote: > > > Could you solve the noise issue with a phase-locked loop? THis takes > > advantage of the fact that the spindle has momentum and the > > accelerating forces are limited. > > > > It is a common technique in electronics, you build a good, clean local > > oscillator and then take your frequency measurement from that, rather > > than from the noisy real-world data. But at the same time, you > > compare the phase of the local oscillator with the real data and make > > tiny adjustment to the local oscillator. > > > > What is really happening is that you only look at edges if they happen > > near the expected time and weigh them, scoring to how near the > > expected time so statistically almost all the noise is ignored. > > > > You can try averaging, but it does not work nearly as well and has a > > long lag. > > > That I have tried, taking the sum of the last 4 edges, but the lag was > showing and it was still too noisy to work well. > > > On Wed, Jul 21, 2021 at 1:19 AM andy pugh <bodge...@gmail.com> wrote: > > > On Wed, 21 Jul 2021 at 05:36, andrew beck <andrewbeck0...@gmail.com> > > > > > > wrote: > > > > Andy what do you think is the max rpm that this will read reliably > > > > do you think? > > > > > > It will handle a higher speed than a full quadrature setup as it > > > only needs to see one edge. > > > I have run it up to 16000 rpm (in the video) with a 50,000ns base > > > thread. > > > > > > The problem with counter-mode is noise rejection, noise is seen as > > > pulses and gets added to the position. (This isn't unique to the > > > missing-tooth index, this is counter-mode in general) > > > > > > -- > > > atp > > > "A motorcycle is a bicycle with a pandemonium attachment and is > > > designed for the especial use of mechanical geniuses, daredevils and > > > lunatics." > > > — George Fitch, Atlanta Constitution Newspaper, 1912 > > > > > > > > > _______________________________________________ > > > Emc-users mailing list > > > Emc-users@lists.sourceforge.net > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > 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) > 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 > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
