Hello! Curious if anyone else has had problems with larger UAV frames and autotune, and if so, have you found any fixes to prevent crashes?
We’re running into an issue with Autotune on a large quadcopter (16" props).
- Autotune worked beautifully and the drone appears to fly perfectly afterwards, with logs showing minimal vibration and almost perfect roll/pitch rate tracking.
- It flies perfectly in altitude hold mode and appears to fly well in position hold with autotune
- In certain cases the drone goes into unstable oscillations and crashes with the autotune PIDs (e.g. a client immediately gave it full left roll, then full right roll, then no roll and it goes into an increasing oscillation and crashes)
The only solution we’ve found for them is to reduce all gains by about 50% and make the drone substantially less nimble and limiting the maximum rate on pitch and roll axes and various MPC settings to reduce aggressiveness.
We have the UAV back for repairs and it flies much worse than it did with autotune settings, so trying to find a crash-proof middle ground before we send it back.
Thanks in advance for any ideas or suggestions!
I’ve had limited luck with autotune on big frames. In tuning 900mm class (22” prop X-frames) I’ve found success in taking default PIDs for frame class, going straight to MC_PITCH_P (and ROLL_P) and halving the P gain value. That removes the bad behavior for me and acts as a starting point to tighten back up from there. I generally end up around .6x initial default P gain value in the Attitude Controller tab and up a few ticks on master multiplier in Rate Controller tab.
Every build is different on filtering and vibes so it’s not a fire and forget tune. I’m not a pro by any means but I’ve generally found that the P gain needs to come way down on the big boys.
Yeah, that’s what we’ve found too. Generally much lower P values help a lot. It’s too bad that autotune doesn’t have any settings or adjustment for prop size, as it works great on smaller builds but fails once you seem to get to 12" or larger.
Appreciate hearing your experience!
@bresch Anything we can advise/improve for autotune with large props here?
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Any improvements would be appreciated! The issue seems to be that there is a lot more inertia with large props, which the system sees as unresponsive and tries to fix with very large P gains. Then during flight, those large P gains cause overshoots when large movement is demanded, leading to crashes from increasing oscillations.
At least that’s what we’re seeing in our logs.
