Re: Re: Closed loop steppers

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.