[time-nuts] LTE-Lite module
phk at phk.freebsd.dk
Tue Oct 21 06:41:07 UTC 2014
In message <766D6811-F733-4AB2-8574-24E4606E45FA at aol.com>, Said Jackson via tim
>Thats exactly right Bob.
>By the time your ocxo jumps to catch up to the efc voltage, you
>have oversteered, then the process starts in reverse and the ocxo
>jumps in the opposite direction.
This is a well known PI effect called "windup".
The cause is a phase offset of opposite sign of the frequency offset.
The fix is simple:
Start running with only the P term, and engage the I term only after
1. The input phase offset changes sign
2a. The input phase offset levels off
2b. Some calibrated amount of time has passed.
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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