[time-nuts] New Subscriber, DIY GPSDO project (yes, another one)

[Attila Kinali]

On Mon, 09 Mar 2020 21:31:00 +0000
"Poul-Henning Kamp" <phk at phk.freebsd.dk> wrote:

> >Please correct me if I'm wrong, but that sounds like a
> >simplified version of a Kalman filter, with the only
> >predicted variable being the frequency of the LO.
> 
> I think this has many names.

Definitely. If you leave out the predictive aspect, then,
for the phase/frequency case of an GPSDO, the loop
formulation becomes a PI loop (unless I misunderstood
someting). If you take frequency drift into account,
it becomes a PII² loop.

> I'm not sure a Kalman filter would really do much extra for the
> basic GPS+(OCXO|RB) case, unless you get advanced and also feed it
> temperature and air pressure.

Kalman filters are just a formalism to map a system model into
a control loop that predicts the internal states of the model
and gives a more optimal control using this predictive power.
You can map any PID loop back to a Kalman formalism.

			Attila Kinali 

-- 
<JaberWorky>	The bad part of Zurich is where the degenerates
                throw DARK chocolate at you.