At 08:30 AM 2/13/2008, you wrote: >Am 13.02.2008 um 11:41 schrieb [EMAIL PROTECTED]: > > > On 12 Feb 2008 at 18:03, [EMAIL PROTECTED] > > 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. > > > > > > Did someone rewrite the spec for PID? > >No, but steppers are different ;-), normally, PID works with a output >signal from 0 to +-100%, but steppers are working as steppers, this >mean, they "only" can do steps and not power. (I hope i can explain >it clearly). >The only way i could think to overcome this problem, is a logic in >between EMC and the stepper driver who convert the PID output to more >(and faster) or less (and slower) steps to the stepper driver. But >still, if the stepper motor looses steps, the stepper is running out >of sync, and would not come back, especially if you tries >"harder" (more and faster steps). > >I could only recommend use servos with digital scales, or steppers >without. >I have seen some steppers with resolvers and feedback logic >integrated, they could also behaves like servos, but still, then I >would go to "real" servo drives. > >Hansjakob
Depends on which control loop is being discussed. If in the position loop then the output of the PID calculation is a velocity command and will work with steppers just fine. If in the velocity loop then the output is torque command and is of little use with steppers. __________ Andre' B. Clear Lake, Wi. ------------------------------------------------------------------------- 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
