Isn't that very dangerous? If I have a ball screw with 10 mm pitch and my encoder shows 1°, and is moved -2° it will stand at 359° , so how will you know witch turn is the correct one?
The final position can be 10 mm wrong, or do I understand that wrong. Norbert Am 05.01.2017 um 00:16 schrieb Rene Hopf: >> On 4 Jan 2017, at 19:07, Nicklas Karlsson <nicklas.karlsso...@gmail.com> >> wrote: >> >> As I understand it position is already known from absolute encoder so there >> is no need to run machine to a switch is hit? > there are generally 2 types of abs encoders: multiturn and non multiturn. > non multiturn encoders only give the absolute position to 0-360 deg, so one > shaft revolution. > if you turn it 5 times, the encoder cant tell without power. > multiturn encoders usually have a battery backup, and can count multiple > turns when powered off. > with multiturn encoders its really easy, you just have a fixed offset to your > home position, and it just works. > the idea is to use non multiturn encoders in a multitun way, so you just have > to remember on which rotation the servo is, but not where on that rotation. > so when you assume your motors dont turn more than a full revolution while > the machine is powered off, you can just use the abs position, and full > revolutions to work out the exact position. > of course this also works with resolvers. > >> >> On Mon, 2 Jan 2017 22:00:41 +0000 >> andy pugh <bodge...@gmail.com> wrote: >> >>> Due to the lack of an M3 die that actually cuts a thread, and the fact >>> that none of the places that sell dies on a bank holiday sell dies of >>> a quality that I feel like buying, I spent today trying to make my >>> lathe home without moving. (with a complicated setup on the lathe, >>> maybe including a steady-rest, this can be a good feature) >>> >>> The idea is that by saving the machine position to file I can then use >>> the absolute single-turn resolver position for fine-position >>> determination and the saved position to work out how many full turns >>> need to be added to that. >>> >>> Adding the resolver position to the full-turns position gives me a >>> value that I can pass to motor-pos-fb (and, it turns out, pid.fb) such >>> that when the "home" button is pressed with HOME_ABSOLUTE_ENCODER = 2 >>> set in the INI (a new feature, thanks Dewey) the machine adopts the >>> current position as the true position. >>> >>> I do this with a user-space python component (as it needs file system >>> access) and it writes its own little file. >>> >>> I am trying to determine if I can use the existing position.txt file. >>> The file itself is ideal, my file ends up with exactly the same data, >>> but I think that if that file exists then the values are copied >>> directly into joint.N.motor-offset and that isn't _quite_ what I need. >>> >>> -- >>> 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, 1916 >>> >>> ------------------------------------------------------------------------------ >>> Check out the vibrant tech community on one of the world's most >>> engaging tech sites, SlashDot.org! http://sdm.link/slashdot >>> _______________________________________________ >>> Emc-developers mailing list >>> Emc-developers@lists.sourceforge.net >>> https://lists.sourceforge.net/lists/listinfo/emc-developers >> ------------------------------------------------------------------------------ >> Check out the vibrant tech community on one of the world's most >> engaging tech sites, SlashDot.org! http://sdm.link/slashdot >> _______________________________________________ >> Emc-developers mailing list >> Emc-developers@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/emc-developers > > ------------------------------------------------------------------------------ > Check out the vibrant tech community on one of the world's most > engaging tech sites, SlashDot.org! http://sdm.link/slashdot > _______________________________________________ > Emc-developers mailing list > Emc-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-developers ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
