Autotune failed / Pixracer / overpowered

@Thorsten wrote:

Hi Leonard and all,

I am building a new quad based on the PixRacer. The copter is a little overpowered, vibrations are very low, and it flies stable and quite ok after some manual tuning. Now I tried Autotune and for the first time I am having problems with it. After Autotune the copter was more than sluggish and crashed because it was not controllable (nothing broke so all fine).
What is strange is that the manual tuning values acutally look too high to me for a 400mm copter with 900kv motors and 1.2kg (without payload). Yet, it flies ok. In contrast the Autotuning PIDs are very low. When tuning it manually I had to increase the ATC_ACCEL_P/R_MAX values to >=100000. Then it was responsive and not sluggish. Autotune returned ATC_ACCEL_P/R_MAX values around 13000.

Question: do you have any ideas or recommendations I should try? The copter drifted a bit and there might be a small COG imbalance. However, both pitch and roll failed pretty much the same way. So it seems tuning was somehow successful. But since it is unflyable I am wondering what went wrong.
I'll try an autotune again with payload the next days (after it stopped raining...).
You find the log file at: http://thorstenbehrens.de/AT.zip

Thanks and best regards,
Thorsten

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