Prompted by a query on the forums on the age-old question of using encoders with steppers, I started wondering about wierd and wonderful ways to make it work.
The issue is that steppers just don't have the right characterstics to work in a servo loop, as trying to run them harder to recover a missed step will probably make things worse. So, I pondered the idea of using a PID with a unity feedforward term and a negative PGain, so that as long as there is no error the system works as a normal stepper setup, but if there is a missed step then the error * Pgain would back the velocity off a bit. I think the drawback of this is that there is nothing to claw the error back, though perhaps a slow I with a higher limit than the P might do it. Probably a more promising idea is to not attempt to recover position immediately, but to link the output of a PID to the motion.adaptive-feed pin, so that any missed steps result in the system backing-off the feedrate.You would probably want a slow-I PID as a separate component to claw back the missed steps once the feedrate has slowed enough. Any thoughts? -- atp "Torque wrenches are for the obedience of fools and the guidance of wise men" ------------------------------------------------------------------------------ Increase Visibility of Your 3D Game App & Earn a Chance To Win $500! Tap into the largest installed PC base & get more eyes on your game by optimizing for Intel(R) Graphics Technology. Get started today with the Intel(R) Software Partner Program. Five $500 cash prizes are up for grabs. http://p.sf.net/sfu/intelisp-dev2dev _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
