On Friday 09 August 2019 05:59:46 andy pugh wrote: > On Fri, 9 Aug 2019 at 06:30, nkp216 . <[email protected]> wrote: > > Question on servo tuning. > > there is such an opinion: > > > > "I don't think deadband is useful > > in velocity mode. You will always get dithering between adjacent > > counts - deadband just makes it dither across a bigger > > discontinuity." > > It isn't clear to me if we are talking about a velocity PID (velocity > command out, velocity feedback in) or a position/velocity PID > (velocity command out, position feedback in) > I can see the statement quoted being true in the first case. > > It might well be true in the second case too. That's a post from a > long time ago, but the fundamentals of PID have not changed much.
What I'd like to see, is a better discussion that connects velocity commands fedback with velocity info which is in fact a variable voltage on an instant basis. And the same for position systems that explains the difference. Looking at the schematic is helpfull, but even that can be ambiguous. But driving the relatively light mass of a speaker cone as opposed to a motor armature that can weigh pounds brings in a much higher mass, meaning inertia, and that complicates things no end. Somewhere, there has been penned, a one sentence definition that clarify's it all. But I can't recall ever seeing it. Thats pretty simple for the case of driving a speaker, if only moderately understood by this viewer, whose background in feedback systems in general has been gleaned from the techniques used for analog sound where one can have distortion products that are 90 db below the level of the audio, and at the height of NTSC video was also used there, with a marked improvement in overall distortion and bandwidth. Texas Instruments has some truly awesome single 5 to 15 volt single supply op-amps intended for NTSC video, with gain vs bandwidth products in the 10 gigahertz range. They, at video speeds, truly were a straight piece of wire with quite usable power gain and vanishingly small phase shifts. 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
