> On 4 Jan 2017, at 19:07, Nicklas Karlsson <[email protected]> > 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 <[email protected]> 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 >> [email protected] >> 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 > [email protected] > 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
