Re: More questions !!

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.

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