On Sunday 01 February 2015 13:41:03 Karlsson & Wang did opine And Gene did reply: > It might simply be because resolvers are analog which considered to be > old technology. It is useful to have some extra resolution above the > accuracy for the control loop and I think resolvers usually have > higher resolution. > > I read many times digital control loops are faster but quite a lot of > digital control loops are a lot slower than the cheapest available > operational operational. > This is why one studies his rockhopper output, to see if the digital data can make it all the way thru the chain of processing modules in one servo thread invocation by changing the order of the addf's in the .hal file.
The delay in that case is fixed, and a direct function of the servo thread frequency. Often, raising the servo thread frequency can go a long long way toward rock solid stability in a spindle speed control circuit. My lathe, now that I have a 5i25 doing the high speed stepper honors, is now running with a nominally 4 kilohertz servo thread, enhancing the effectiveness of the speed servo considerably without instability or overly soft control down to about 250 rpms. Conversely I have purposely inverted that order if I needed a slower responding loop. But be aware of Nyquist phase reversals in that event as they can really enhance a near resonant condition. Basically its best not to allow a phase shift to ever exceed 90 degrees of the system resonant frequency where the gain at that frequency is above one. > > On Sun, 1 Feb 2015 17:49:41 +0000 > > andy pugh <bodge...@gmail.com> wrote: > > On 1 February 2015 at 17:05, Kirk Wallace <kwall...@wallacecompany.com> wrote: > > > I know very little about resolvers, but I think it means that > > > resolvers are analog so one needs to determine what the 100% and > > > 0% signal values are, and values in between (to deal with > > > linearity) to convert to data. > > > > The reader takes the ratio of the sin and cos voltages, so the > > absolute voltage is vaguely irrelevant. > > > > I think what I am saying is that the tendency of folk to immediately > > remove a $1000 resolver and fit a $100 encoder when doing a retrofit > > might be a mistake. > > ----------------------------------------------------------------------- > ------- Dive into the World of Parallel Programming. The Go Parallel > Website, sponsored by Intel and developed in partnership with Slashdot > Media, is your hub for all things parallel software development, from > weekly thought leadership blogs to news, videos, case studies, > tutorials and more. Take a look and join the conversation now. > http://goparallel.sourceforge.net/ > _______________________________________________ > 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) Genes Web page <http://geneslinuxbox.net:6309/gene> US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS ------------------------------------------------------------------------------ Dive into the World of Parallel Programming. The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
