On Tuesday 01 September 2015 16:39:49 J. wrote: > 5 msec is not bad. In the olden days we ran on a 20msec position loop. > > So it will be inertia mismatch. I also battled my but off last year > with a Deckel. > > My solution for encoder noise is an RS485 connection and if it is > still bad a computer screen cable ferrite (or similar) around all 8 > cores of the encoder cable simultaneously. > > Cheers > > J.
Its not cable picked up noise. Its a combination of not exactly a 90 degree phase angle in the encoder disk and interruper mounting, and throw in a thou or 3 of ecentricity in mounting the disk on the spindle, so there is a once per rpm wibble in the detected speed, and the backlash reduction in the mill that carved the disk, The combination can result in instantainius jumps in the output of the encoder of as much as 10% of the actual rpms. Really tight ball screws in the carving machine will reduce it, as will some time on a piece of 600 grit wet-r-dry on a granite plate, wet to smooth away the carving burrs that the interrupter see's as a variation in the slot width. Ditto for some time in a vibrating case cleaner us reloaders use to make our ammo at least as bright & shiney as brand new remchester stuff. If there was room enough to make the disk bigger, the carving machines errors would fade into the noise, but about 2.9" is as big as I can go and still fit it in, and carve 67 slots with a .00315" mill. One longer slot for the index or Z from the encoder. Quadrature related errors are 85% of it, and blending all 4 edges reduces that noise quite a bit. And it appears that any positioning error in a G33.1 rigid tap operation, from the encode lag as it turns around at the bottom of the hole, is well below what it takes to stress a 4-40 or 3mm.5 tap. A 4 slot lag is equ to a 5.37313432836 degree error. Most taps will ignore that. > > Sent from my ASUS MeMO Pad > > Gene Heskett <[email protected]> wrote: > >On Tuesday 01 September 2015 15:35:38 Jan de Kruyf wrote: > >> Gene your filter theory might well be right. Because you add a > >> measurable delay in the loop. > > > >True, but best case is only 5 milliseconds, thats much faster than > > any inertial effects. > > > >> The other thing I found is that the load inertia of a spindle is > >> often badly matched to the motor inertia. This causes a real head > >> ache setting up the pid. > > > >Yes, I'd have to assume that the motors armature is a much larger > > factor in the rotating mass than the spindle itself unless a huge > > multiple edge fly cutter was mounted. The geardown, even in high > > back gear, is at least 3/1. > > > >> Feed forward of the signal might help in both cases, since then > >> the feedback amplification needed is much less. > > > >pncconf set FF0 and FF1 to 1.0, which surprised me too. In my other > >tuning I have quite often used 100 as FF0, meaning 100% of the input > >command is sent to the output as a base. Pgain then is the major > > error corrector, but here its doing almost all of it. FF1 is 1.0 > > IIRC. FF0 is normally used herre to put the error so its straddling > > zero. 1.0 won't do it. > > > >> Cant help you with all the variables you refer to. > >> > >> cheers, > >> > >> j. > > > >Thanks Jan. > > > >[...] > > > >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 > >[email protected] > >https://lists.sourceforge.net/lists/listinfo/emc-users > > ---------------------------------------------------------------------- >-------- _______________________________________________ > Emc-users mailing list > [email protected] > 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) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Monitor Your Dynamic Infrastructure at Any Scale With Datadog! Get real-time metrics from all of your servers, apps and tools in one place. SourceForge users - Click here to start your Free Trial of Datadog now! http://pubads.g.doubleclick.net/gampad/clk?id=241902991&iu=/4140 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
