Re: I-LPT & step/dir servo amps

At 04:01 PM 10/16/99 -0400, you wrote:

>
>I'm happy to see some discussion about Indexer LPT, even though it *is* a
>for-profit product.

Why should that matter? I see discussion of a number of commercial products
in here.

>interested in hearing about different ways of utililizing it using different
>software and mechanical systems.

I've wondered about that too. I don't see much word on apps. Most of my
contacts have been small lot and hobby machinists, and now and then I get
some interest from the gantry people: waterjets and stuff like that. I
think the product is also used in education as teaching tool perhaps. Give
them a copy and see what they can write. It's so general purpose it can do
any motion task. I'm sure it could run a robot arm and probably hexapod
too. You just have to feed the kinematic output to it, formatted in the
right command set. Saves you writing your own driver software, but saying
that doesn't give it much credit since it's certainly many times as
flexible as most drivers.

>Also, in a related topic: I've asked here before (with little response)
>about step/direction-input servomotor amplifier systems such as the one
>Camtronics sells.
>
>What would it take to match the performance of a "standard" servo system,
>using step/direction output? I've looked into this a little, and it seems
>one issue is closing the loop with an equivalent, high-performance PID
>algorithm.

I thought they servo part had it's own feedback, from scales or encoders,
no? Then it simply moves proportional to the number of steps you giv eit.

> Another issue is resolution - you would need a fairly high
>frequency step/direction source, I suppose. Would that frequency need to be
>any faster than a good servo loop update rate (for an equivalent machine
>resolution)?

Your servo loop has to update and move move faster than step-count, no?
Else how do you interpolate on two or more axes and get the right shape?

Best wishes,

Hoyt McKagen


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