On Wed, 13 Feb 2008, Dave Engvall wrote: >>>> EMC can do PID just fine. It's steppers that can't. Steppers lose >>>> torque as the speed increases. There is no way around this, it's >>>> just the physics of the motor. >> >>>> PID loop will attempt to correct for a lagging motor by requesting >>>> more "effort" from the motor. >>> >>> When did this become the *only* option PID had, more torque and >>> overspeed? >>> > > rant on: > > Because that is the definition of PID. > > You are not going to like this answer: but if you insist on using > steppers in the performance zone that they are not engineered for then > write a stepper-only module that lowers velocity when following error > starts to increase.
I'd just like to point out that EMC2 can theoretically do this already with the 'adaptive feed' input. An increase in following error would reduce the feed requested by the motion module. This will oscillate without a lot of tedious tuning, or an analytical understanding of the control dynamics. Also, the traditional step/direction interface leaves much to be desired. If you do decide to write your thesis on it after all, please cite me as a reference :) -fenn ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
