Autotune makes plane far less responsive

ArduPlane
1

I flew my new, very heavy (460 g) Nano Goblin plane today in low wind conditions (around 2 m/s). I took off in FBWA mode, then immediately switched to Autotune mode when it was in the air. During the flight, the plane only seemed to get less responsive and harder to control. This is confirmed when I look at the log file (EDIT: I uploaded the wrong log before, this is the right one: 2024-08-12 07-37-45.bin - Google Drive): for axis 0 (pitch?), the P coefficient drops from 0.08 to 0.0036, the I coefficient drops from 0.15 to 0.0036, and FF goes from 0.34 to 0.074, although D shoots up from 0 (?) to 0.004. The same story holds for axis 1, although the drop isn’t as severe. 45 seconds into the flight, I crashed, apparently just because of pilot error (the logs say I pushed the nose down…even though I could have sworn I pulled up). I glued the plane back together and tried to fly it again, but it just fell to the ground instead of taking off after I threw it, likely because the new PID settings made the plane extremely unresponsive.

What am I doing wrong? What are some good default parameters I can set the PID values to for the Nano Goblin so that I can at least fly the thing without crashing and having to glue it back together?

Details of my setup:

FC: Mateksys F405 WMN
Ardupilot version: Plane 4.5.4
Radio controller: RadioMaster TX12 MkII 2.4 GHz
GPS & compass: HGLRC M100-5883

2

You might want to increase the AUTOTUNE_LEVEL. Reset the PIDs to default and try again with a level 7. (6 is default, go up in stages)

https://ardupilot.org/plane/docs/automatic-tuning-with-autotune.html#autotune-level-settings

https://ardupilot.org/plane/docs/automatic-tuning-with-autotune.html#setting-up-for-autotune

3

Thanks, I can try that. How can I find out what the default PID values are? (They may not be the ones I started the accident flight with because I might have activated autotune mode earlier, while testing.)

4

The log you posted doesn’t have any changes to the PID values so that should all be default.

And for what it’s worth, that log never went into autotune. The full log is in FBWA. Update: — I think I’m wrong about this. Hold on.

The throw also looks very steep, and I think the plane probably stalled just after you threw it. The plane should be only slightly nose up when you throw it (5-10 degrees nose up)

5

Oops, I think I shared the wrong log. Can you check out this one instead? 2024-08-12 07-37-45.bin - Google Drive

6

Okay, my bad. I see the Autotune now. I’ve been looking at too many copters… Anyhow autotune didn’t finish so it doesn’t appear to have saved any values. So you’re still on default PIDs.