interpolation and algorithms of multiple axes was Re: Pulse Gen

Hi,

Jon, I respectfully disagree for two reasons:

1) This is based on an idustrial product I originally designed about
10 years ago. It was a dual axis pulse gen integrated with a Z80
computer on the same board to do the math. It was way too expensive
($750) but several hundred were sold. It worked perfectly.

2) It doesn't matter when precisely you output the velocity update,
only that you update every interrupt. The data is "clocked" in on the
interrupt edge. You have the entire subsequent interrupt period to
present the next update.

Mariss

--- In CAD_CAM_EDM_DRO@egroups.com, Jon Elson <jmelson@a...> wrote:
>
>
> I really don't think this will work, if you need to keep track of
absolute
> position. I have thought about this, and it just seems that there
will
> always be an occasional sampling uncertainty that can cause lost
> (or doubled) counts when the step pulse occurs just as the computer
> changes the velocity. Did a step come out just before the change,
> or not? The only way to know is to count them!
>
> So, that is what I had in mind with my rate generator. It would
generate
> both step/dir and quadrature pulses (useful for stepper drivers that
> take phase inputs). The quadrature outputs would be coupled to a
> quadrature encoder counter (in systems without encoder feedback)
> so that an exact position reading would be maintained at all times.
>
> I suppose you could arrange software to forbid a rate that would
put a
> pulse too close to the end of the sampling period, so that the
uncertainty
> could be prevented.
>
> Jon