Re: Accuracy of Step/Dir Driven Brushless Servos

Thanks Eric, I appreciate the information. I get my motors and
drives tomorrow and can't wait to get started.
Mark

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Eric Keller
<unterhausen@y...> wrote:

> I sent you a private email where I answered at least
> part of your question. I'll try again.
>
> You do need to connect the encoder a and b phase
> outputs to both drive and rutex. Obviously, you only
> need to power the encoder from one source.
>
> In general, if an brushless servo motor drive has an
> encoder input, it uses it for commutating the motor.
> The rutex needs the encoder output to close the
> position loop, i.e. each time it gets a step command,
> that is the same as a change in position. It then
> changes the voltage as required to make the motor
> match that new requested position. The drive is using
> the encoder output to make sure that it has changed
> position enough to meet the new demanded position that
> it is getting from the rutex, plus it needs that
> information to know how to commutate the motor.
>
> Having said that, I have a Compumotor OEM650SD that is
> simply a hall commutated torque command drive with an
> added board that does exactly what the rutex board
> does. I believe this technique is quite common,
> although I am hard pressed to think of another example
> right now.
>
> So the simple answer is that brushless drives,
> properly tuned, are able to respond to fairly small
> position input commands, like a step/direction
> controller would request.
>
> My backup plan for my bridgeport is to use step/dir
> inputs to my brushless drives. I don't think that
> there are any significant accuracy issues with this
> setup.
>
> Eric
>
>
>
>
>
>
> Is this a stupid question or something? I am curious
> why no one has
> responded.
> Mark
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "natchamp_87
> <mark@h...>"
> <mark@h...> wrote:
> > I really need some input. Does anyone have any
> experience with
> > driving brushless servo motors with Step/Dir
> signals? My plan is
> to
> > use the Rutex 997 board that inputs step/dir signals
> from the
> > parallel port and outputs the 0-10v signal to my
> Aerotech drives.
> > The Rutex board also receives encoder feedback. My
> question is: Am
> I
> > sacrificing accuracy with this approach? (or
> anything else?) Also,
> > will my encoder feedback go to both the Rutex board
> as well as the
> > drive/amp because the amp has encoder input too.
> Any feedback
> > greatly appreciated!
> >
> > Mark
>
>
>
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