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I have a 10" inch drone that I have trouble tuning. On the default Betaflight PIDs it feels really unstable, and I have tried to raise P, I and D both together and one by one without noticing much difference. Some things I almost doubled even. Since Betaflight is tuned for 5" inch quads (I think); are there more parameters than those three that I should change when tuning a larger quad? Or should I just keep increasing everything?

I should probably also add that I run Betaflight 4.1 with bidirectional dshot and RPM filtering.

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Disclaimer: I don't know anything of the following for sure, so be careful. Be very, very careful.

The PID controller itself does not care whether it's a 5 or 10-inch quad. The PID gains, though, do care, and the Betaflight default preset numbers are for something around 5" size. For instance, for a tiny whoop-size quad the gains must typically be raised 3x or more!

I'd imagine this means that for a larger quad the gains should be several times lower than the default, although I have no way of confirming this. In any case, having low PID gains doesn't promote dangerous behavior from the quad, so it's safe to start by cutting the default gains in half or even 3x and working from there. I'd also predict that a bigger quad, having more inertia in both the motors and the frame itself, will need larger feedforward gains to feel responsive than a typical 5".

Another option would be to try and google some published PIDs for a similar-size quad, although that might be a dangerous proposition if you just copy them.

In any case, start from a safe number (it's a 10 inch, so be safe. be very safe) and slowly work your way up. Analyzing the step response in BlackBox logs to gauge the direction in which you need to tune is probably a good idea as well.

The other place you should look at is the filtering tab, as a larger quad naturally has lower characteristic frequencies. It's great that you run RPM filtering, but take a look at the regular lowpass filters as well, you might want to lower the cutoffs for them. You may want to look at your BlackBox logs here as well to decide.

Other than the radically-different gain numbers and possibly playing with the filters, though, the configuration shouldn't be all that different. Good luck, and stay safe.

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  • Good point! He may even want to look into RPM filtering instead of tuning the dyamic notch filters. – ifconfig Apr 20 at 3:58
  • Thanks. I didn't even think about the filters! – Hannes Hultergård Apr 20 at 5:46

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