[time-nuts] D term (was no subject)

Poul-Henning Kamp phk at phk.freebsd.dk
Mon Jan 26 12:44:23 EST 2015

In message <CAMQqFumOdB4gcFfQjQ_nced0C_U=FBMyOFwL7VuXM8WoTqGHMw at mail.gmail.com>
, Didier Juges writes:

>In order to automatically compensate for different oven loading (and
>ambient conditions), the controller injected a very low level "random"
>noise over the temperature setting and by analyzing how that noise was
>filtered by going through the oven, was able to determine the response of
>the oven itself and from that optimize the PID terms in real time as a
>function of the load. This was in the early 80's. It was pretty hot stuff
>then, even for an oven :)

Many off the shelf temperature controllers have an "auto-tune" button
these days which does exactly that:  Inject a heat-pulse, see what
happens, do math...

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

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