Re: servo control

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Binoy Shenoy
<binoyshenoy@y...> wrote:

> I am talking about keeping the motor fixed in a certain position so

that it does not move. This is when it is not in motion.

Binoy, The over simplified answer is that a servo is a DC motor and
the current depends on the load. So at rest with no load, the current
is near zero. But if a torque (load) is applied to try to move it
away from it's position then it will draw whatever current is
required to resist that load. Whether it is stopped or moving makes
no difference, the same rule applies. Jon's answer explains why this
is so.
al

>
> Jon Elson <elson@p...> wrote:
>
> binoyshenoy wrote:
>
> >How does a servo motor lock in place? What kind of excitation

should

> >be given by the drive?
> >
> >
> An encoder senses position, and the drive or computer sends a

correction

> signal if the motor drifts off position. Some servo drives also use

a

> tachometer
> that allows the velocity to be kept constant even between encoder

updates.

>
> For a brush DC motor drive, there would be a voltage applied to the

motor

> to get motion in the proper direction.
>
> Jon
>
>
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