mak24

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High PID Values
« on: May 24, 2017, 02:13:08 am »
I finally have a stable Quad with a working GPS. 

Using Autotune to get the PIDs tuned, I have been getting very high PID values.  Please see the screenshots attached.

I have flown very successfully with these PID settings.  I do check the motors after 2-3 minutes of flight and the motors are comparably as hot as with stock PIDs.

Is this possible to fly with high PIDs without adverse results?
mak24

My Quad Build
Alien 450
Emax 25 Amp ESC
2212 980 KV SunnySky motor
10*4.5 APC Props
Revo FC
GCS 16.09 Rhino

Re: High PID Values
« Reply #1 on: May 24, 2017, 05:54:57 am »
Inner Loop PIDs look similar to some of my AutoTune PIDs.  Outer Loop look just a little higher than mine, but that sort of variation is to be expected.

If it flies smoothly and for the same length of time as lower PIDs and with motors about the same temperature as with lower PIDs then they sound good to keep.  :)  All of those are important because if PIDs are too high (especially the D term?) you can get "invisible oscillations" that are so small and fast that you can't really see them, but they will make motors hot and reduce flight time.

You want the PIDs to be as high as possible, so it corrects errors as quickly and certainly as possible.  For instance, the highest PIDs give the best, most stable flight when descending straight down, through your own downwash.

If it is smooth (no jitters) but reacts too quickly for you, then you should reduce "Response" on the settings page (Basic or Advanced tab).  Do not reduce the PIDs just to slow down the response!

If you set up a SmoothQuick AutoTune slider you can adjust the PIDs from smooth to quick in flight.  If you see it climbing a little with the slider towards quick, that indicates probable "invisible oscillation" and you should run it closer to smooth.  I generally move the SmoothQuick slider towards smooth, set the throttle stick (manual thrust mode) to hold altitude, and then move the SQ slider towards quick and back it off a little from when I can see a slight climb at the quick end.

mak24

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  • 55
Re: High PID Values
« Reply #2 on: May 25, 2017, 08:23:09 pm »
Thanks for the quick response and apologies for my tardiness.  work stuff you know  ;)

Thanks for allaying my fears for the Inner loop.  Outer loop are the default / stock values.  (Note: to self - check what are inner and outer loops).

It is smooth, but sometimes I see jitters.  I will keep re-running the Autotunes and see if I could get an average value as I am seeing differences during different episodes of auto-tuning.

Great tip about Smoothquick.  Will look into it and report back.

Thanks once again, TheOtherCliff

I am totally hooked.  Long live Librepilot
Stay Well  :)
« Last Edit: May 25, 2017, 09:28:00 pm by mak24 »
mak24

My Quad Build
Alien 450
Emax 25 Amp ESC
2212 980 KV SunnySky motor
10*4.5 APC Props
Revo FC
GCS 16.09 Rhino