Does autotune just generally not work well with large copters that have low KV motors?  (using 6S, 320kv, 17x5.5 CF props).  Honestly I think it flew much better with the default settings than what autotune found for it...and the yaw is super slow and delayed.  Is this just common with large hex's and the pixhawk? Anybody have experience with this frame and care to share the PIDs that work for them so I can at least have a good starting baseline?

Failing that, any suggestions on how to improve it? Especially yaw performance... it suckeths. Tuning large copters is hard because I really don't want to crash this thing... Using copter 3.3 fwiw.

Thanks!

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I've never had "great" results using Auto-tune to be honest on ANY sized flying lawnmowers. I have found that if built correctly the closer to stock pids I run the better it flies. On my T960 with 320kv motors @ 17.5 CF props it flies PERFECTLY on stock pids so that is where I leave it. Last thing I want to do is tank that sucker :) And since it flies so well @ stock there really isn't any reason to use an auto-tune.

Instead of auto-tune put everything back to stock, then set up one of your pots to ch6 and then just adjust it until your happy with yaw and then leave that # there.

http://ardupilot.org/copter/docs/ac_rollpitchtuning.html

http://ardupilot.org/copter/docs/tuning.html

Thanks Craig!  I set the PIDs back to default and the roll/pitch is quite good with standard parameters.  I messed with the ch6 tied to yaw P and D and it's a bit better now (at least I could see it making a difference), but still nowhere near as responsive as my smaller quads.  When the gain was too low it'd drift a lot, as expected, when it was too high it'd still move relatively slow and delayed but would get kinda unstable when centering the stick.  Maybe that's just how big hex's with large efficient CF props are?  'Pretty happy with it otherwise - rock solid position hold and smooth roll/pitch response.

There is a large difference between  say a 550 hex and a 900+ hex. Not that I have flown either plane, but I always refer to smaller multirotors as small and nimble and is like flying a P51 mustang or big and stable is like flying a B52 bomber. VERY different roles and flight characteristics :)

my 690 hexa´s pid´s goes way off with autotune. Tried the AT many times and allways without succes.

It flies quite nice with defaults, just little finetuning with "save trim" feature and some other minor changes on parameters.

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