Re: Low cost Servo Controller

The analog encoder to digital converter is commercially used.

For example Anorad's Anomatic 3 with the 256X option board and Aerotech also has a 256 X option plugin. I have worked on many of
the Anorad CNC's and they work just fine. By the way, Anorad also has an "Interferometric" plugin for extreme accuracy.

The Anorad CNC system is capable of controlling up to 12 axes and at at acceleration to 4g and speed to 60" per SECOND. If the 256X
option is used, the speed is limited to 10" per second.

They often use linear motors and the servo amp size goes up to 150V at 30 Amps

Bertho
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> Jon Elson <jmelson@...> wrote
>
> Bertho Boman wrote:
>
> > From: Bertho Boman <boman@...>
> >
> > Hello Jon,
> >
> > Another way to get high resolution from an encoder is to use them as an analog transducer. If you look at the raw output from
> an encoder, linear or rotory, before it goes into a comparator, you will see that it is gradually varying from a minimum to a
> maximum and then back to a minimum. If the gratings and electronics are designed properly, the output will resemble an offset
> sine wave. That sine wave is feed to an A-D converter that converts it to "higher resolution" digital output.

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>
> Sure, the concept is simple. But, it would have to produce results at a very rapid rate (equal to the servo update rate if
> synchronized, otherwise several times the servo update rate) to simulate a digital encoder. That is what had me a bit worried.
> Could you build one of these interpolator boxes that would keep a 2, 5 or even 10 KHz servo loop stable? The interpolators used
> with inductosyn and resolver systems (like AD2S82) use a phase locked loop, which is always going to follow the encoder with some
> delay. If the delay varies with acceleration, for instance, it could cause servo instability.
>
> Jon