Re: [CAD_CAM_EDM_DRO] Re: Re: GeckoDrives.. Can anyone Help?

mariss92705@... wrote:

> Hi,
>
> I have been following this servo debate on the virtues of a
> tachometer versus discrete steps at low speeds. Unless I have
> misaprehended a basic concept (not uncommon for me), I think it is a
> distinction without a difference.
> An error in velocity translates into a position error over time. As
> speed approaches zero, the time between encoder edges increases.
> Since there is no position feedback between encoder edges this error
> will become large.

Not exactly. The error will never get larger than the encoder resolution
(+ or - one count). The lack of encoder counts means the machine has not
moved suddenly away from where it was when you last got an encoder
count.

> Comparing the two, tach feedback will result true diagonal moves
> (monotonic, or continuous motion) at very low speeds but there is no
> increase in accuracy. That is still determined by
> encoder "granularity".

I never suggested it will increase position accuracy, just that it will give
smoother motion at low speeds. That CAN be important in fine finishing
of parts.

Jon