Re: Re: Closed loop steppers

The beauty of a servo drive is that it will crank up to max available torque
to get to where it is supposed to be, and keep trying until it gets there
(or something smokes).

cvl

----- Original Message -----
From: Ian Wright <Ian@...>
To: <CAD_CAM_EDM_DRO@onelist.com>
Sent: Monday, January 17, 2000 5:03 PM
Subject: Re: [CAD_CAM_EDM_DRO] Re: Closed loop steppers


> From: "Ian Wright" <Ian@...>
>
> Thanks for the explanation Ray. I still feel a bit uneasy about the idea
of
> using a 'free running' motor as a servo really is to get ultimate
accuracy.
> While I can see that missing steps on a stepper system could be easily
> overcome by using a suitably sized motor, I don't quite understand how a
> servo system would avoid stalling if it hit a tough bit as it was ramping
> down to a stop - or do the servo boards all use some kind of pulsed power
> feed to maintain maximum torque at such slow speeds - if they do then
surely
> they are going to jerk as much as a stepper in half or microstepping mode?
>
> Ian
> --
> Ian W. Wright
> Sheffield UK
>
>
> ----- Original Message -----
> From: Ray Henry <rehenry@...>
> To: <CAD_CAM_EDM_DRO@onelist.com>
> Sent: 17 January 2000 14:23
> Subject: [CAD_CAM_EDM_DRO] Re: Closed loop steppers
>
>
> > From: Ray Henry <rehenry@...>
> >
> >
> > Ian
> >
> > There are trade-offs between steppers and servos.
> >
> > With steppers, one problem is lost steps. This is what Arne and a few
are
> > mulling over. A second problem is repetitive starting and stopping
rather
> > than simple smooth velocity control. This leads to problems with
> resonance
> > and such.
>
>
>
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