[time-nuts] I've designed a GPSDO, but how "good" is it?

Nick Sayer nsayer at kfu.com
Mon Aug 17 17:37:58 EDT 2015

> On Aug 17, 2015, at 12:49 PM, Nick Sayer via time-nuts <time-nuts at febo.com> wrote:
>> On Aug 17, 2015, at 12:07 PM, Attila Kinali <attila at kinali.ch> wrote:
>> You really should read the wikipedia article on the PID loop and implement
>> a simple PI loop (no need for the D part). That's not more effort than what
>> you already did, but gives you better stability.
> I’ve done PID before (for a reflow oven controller), but thought that the current code was easier to understand. I’m going to try the GPSDO simulator and see how it matches up. It’s entirely possible that an improvement could be made in the time-to-lock, but the steady state performance appears to my eyes to be as close to optimal as I could envision. But I’m new at this, so it’s entirely possible that I’m not looking at it correctly.

I thought some more, and in principle, I could use the 100 second sample error as the proportional and 1000 second cumulative error as the integral. What I wanted to insure with my hand-coded decision making was that the system was not completely insensitive to momentary excursions in the steady state, but that it didn’t overreact. I suppose that could just mean that Kp = 1 and Ki =~ 2 or 3.

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