On Wednesday 06 April 2016 04:53:54 Marshland Engineering wrote: > I finally have my mill table moving under CNC control. > > I'm using a 70 volt supply with DCM D6 drives in Torque mode, Mesa > 7i48 cards, Linear scales for position and 1.2 kw DC brush motors (my > guess on the power as they are 90 volt motors but no current rating) > > The only way I can get any control over the travel is setting P = 0.5 > which of course makes the position accuracy poor. Any more P and I get > sever oscillation. With the size of motor and the 1m table, there is > quite a lot of inertia in the system.
There must be a huge time lag in the feedback. You mentioned linear scales as the feedback source, and many of those, while accurate, are not (from previous postings I recall) close enough to real time. Feedback I am convinced, needs to be from a rotary encoder on the motor that best outputs in A/B/Z format, which by its nature is real time but may lack the ultmate accuracy needed as its discrete steps may not be sufficiently fine. > Anyone suggest starting values or any other suggestions to get this > under control. There is a couple write ups in the wiki that describe ways to merge the use of two feedback signals to do that, IIRC one is set for position, the other set to be velocity, but see the wiki as my wet ram may not be recalling the details that well. > Thanks Wallace. > I didn't note till now that you were addressing Wallace. 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
