Re: Arrgh - the servo vs. stepper debate reawakens!
Posted by
Jon Elson
on 2001-03-20 22:32:58 UTC
dave engvall wrote:
stepper is going. Also, it is practically meaningless, as a stepper CAN NOT
move smoothly - it HAS to move in steps. This is somewhat blurred with
microstepping, but it is still discrete. I can't imagine a practical system with a
DC tach and steppers. It just seems to be going too far out on a limb, when
a servo system is called for.
Of course, in some senses, a microstepping drive and a DC brushless servo
drive actually have a lot in common. Truly, the number of poles on the
motor is the only difference.
Jon
> Ray wrote:No, you don't need a tach on a stepper. You already KNOW how fast the
>
> >
> > <snipped from Jon E>(and from Ray):
> > The advantage to a true velocity servo, straight from the computer, is that
> > the VELOCITY is not quantized by the resolution. So, at very slow speeds,
> > the motion remains smooth.
> > <eos>
>
> But this implies analog feedback via a tach. I suppose you could put a tach on a stepper but the output would be almost as bad as
> an encoder. Maybe some kind of adaptive filter would fix that ...but I thinking pure blue sky.
stepper is going. Also, it is practically meaningless, as a stepper CAN NOT
move smoothly - it HAS to move in steps. This is somewhat blurred with
microstepping, but it is still discrete. I can't imagine a practical system with a
DC tach and steppers. It just seems to be going too far out on a limb, when
a servo system is called for.
Of course, in some senses, a microstepping drive and a DC brushless servo
drive actually have a lot in common. Truly, the number of poles on the
motor is the only difference.
Jon