Hi Eric! On 26.08.2017 22:48, Eric H. Johnson wrote: > Jon, > > ... > > After doing this however (and possibly other config changes I have made along > the way), I am getting persistent following errors. > > At the moment they always occur at head lifts / drops, when X and Y have > basically come to a stop. Head lifts are performed by an air cylinder and > give the system a bit of a jerk. Mostly I am now getting following errors in > X and A. > > I cannot reproduce this with individual MDI moves, for example. I set the > following errors in the config absurdly high, but does not seem to have any > effect. Watching the joint ferrors with halmeter or halscope shows these > ferrors to rarely exceed 0.01". My positional accuracy is quite good too, > hitting end points within 0.001 or 0.002 at worst. >
As far as I remember, there are two kinds of following error tolerance. One is the velocity-dependent tolerance FERROR and then there's the static MIN_FERROR, which is used when a joint is in position (or moving very slowly). In case you did only extend the former, that would not have changed anything for the described problem when the joints are not moving. Bye, Philipp > Regards, > Eric > > On August 26, 2017 3:15:02 PM EDT, Jon Elson <[email protected]> wrote: >> On 08/26/2017 12:39 PM, Eric H. Johnson wrote: >>> Andy, >>> >>> Yes, as TYPE = ANGULAR in the joint section. >>> >>> As for P, yes that would seem to agree with what I am seeing. >>> >>> I made some headway by starting at 24000 counts per degree (actual >> counts per revolution). Tuned that in, then did the same at 1000, 500, >> 250 and 125. Still struggling at 66.6666. Can get it to run slowly, but >> goes unstable at speed and sometimes when nearing the end point. >>> >>> >> Yes, the problem with the PID is that when the scale value >> going in is very low, the jumps in the user units when the >> encoder or step count changes by one is much larger. Since >> position is quantized by either step count or encoder >> counts, there isn't a whole lot you can do about this. The >> best is to set the FF1 as closely as you possibly can with P >> and D very low, use FF2 (with real servos only) in tiny >> increments to help with acceleration, and then raise P until >> the error is acceptable. D should be at the minimum you can >> live with, as increasing D just amplifies the encoder count >> jumps. >> >> Some systems have velocity estimation that tries to smooth >> out the velocity jumps caused by this. If you are NOT using >> velocity estimation where it is available, I think you will >> find it helpful. >> >> Jon >> >> ------------------------------------------------------------------------------ >> Check out the vibrant tech community on one of the world's most >> engaging tech sites, Slashdot.org! http://sdm.link/slashdot >> _______________________________________________ >> Emc-users mailing list >> [email protected] >> https://lists.sourceforge.net/lists/listinfo/emc-users >
signature.asc
Description: OpenPGP digital signature
------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot
_______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
