On Sat, 31 Mar 2012, Dave wrote: > Date: Sat, 31 Mar 2012 14:20:19 -0500 > From: Dave <e...@dc9.tzo.com> > Reply-To: "Enhanced Machine Controller (EMC)" > <emc-users@lists.sourceforge.net> > To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> > Subject: Re: [Emc-users] Trajectory planning and other topics from a, > EMC(LinuxCNC) newbie (TheNewbie) > >My experience with steppers is that once you lose sync with the rotor at >speed, you have to slow down tremendously to regain sync with the rotor. >So once you start slipping, you are pretty much done as you have lost >control of the motor. I don't see how using encoders with steppers >really helps other than detecting when you have lost control of the motor. > >Dave
If you have high res encoders and a high enough loop rate (say 30 -50 KHz) and a PWM sine/cos drive, you can run step motors as 50 pole 2 phase servos, they can never lose steps (as the drive phase is always synced to the rotor) and they have ~0 input power at ~0 load torque. However the driver circuits are more complicated than 3 phase PMS servo motors (4 1/2 bridges vs 3 1/2 bridges) and you have still have the same torque/vs speed curve as with a normal step drive so unless you need something the the step motors provide (low speed torque maybe) step motors make fairly lousy servos Peter Wallace Mesa Electronics (\__/) (='.'=) This is Bunny. Copy and paste bunny into your (")_(") signature to help him gain world domination. ------------------------------------------------------------------------------ This SF email is sponsosred by: Try Windows Azure free for 90 days Click Here http://p.sf.net/sfu/sfd2d-msazure _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users