On Sun, 4 Jan 2009, Roger wrote: > Date: Sun, 4 Jan 2009 06:17:04 +0000 (UTC) > From: Roger <[email protected]> > Reply-To: "Enhanced Machine Controller (EMC)" > <[email protected]> > To: [email protected] > Subject: [Emc-users] A wish - Closed Loop Steppers > > It's unfortunate that there isn't a way to approximate closed loop control > with > steppers and encoders in EMC2. I have read that EMC2 can detect a following > error using steppers with encoders and trigger a fault which is great but this > doesn't really allow the use of steppers in larger or high performance > machines. > > It would be great if you could run a stepper like a brushless servo. Steppers > and drivers are cheap and easy to interface.
We have some experience doing this but IMHO it is of somewhat questionable value. To actually work as a servo requires a high resolution encoder to get reasonable _electrical_ angular resolution. We had direct control of the two phase currents (vector drive). Controlling the feedback with steps would be harder (and inefficient as torque is applied when not needed) Also step motors make poor brushless servos, mainly because they have too many poles (50 versus 2 to 8 for most brushless motors), resulting in too-high drive frequencies and consequent loss of torque at high speeds. For EMC to do this it would have to run a servo loop at the ustep rate, adjusting the rate as needed. It would also help if the number of micro steps were greater than 10. Not impossible but not a trivial task, requiring very fast I/O. > > Roger > > > ------------------------------------------------------------------------------ > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
