Vibrations and high IMU_GYRO_CUTOFF

PX4 Autopilot Multicopter 🛸
1

Hi,

I was test flying with Holybro X500, Pixhawk 4 mini, px4 and experienced heavy vibrations.

After some Investigation I found out that the parameter IMU_GYRO_CUTOFF was set to 80Hz in S500 frame setup, which is much higher than the default value (=30Hz).
FFT Graph for reference. (IMU_GYRO_CUTOFF 70Hz)

bokeh_plot
bokeh_plot840×336 62.9 KB

I Lowered the cutoff to 40 Hz and flew again:

bokeh_plot(1)
bokeh_plot(1)840×336 47.9 KB

And after seeing that the threshold was just above a peak at 38Hz~, I lowered the thresholds of IMU_GYRO_CUTOFF and MC_DTERM_CUTOFF again to 30Hz:

bokeh_plot(2)
bokeh_plot(2)840×336 27.5 KB

And the vibrations were gone, but I have a few questions:

1. What are the consequences of setting these two thresholds to 30Hz? Btw 30Hz is the default value of px4, which leads me to my second question.
2. Why when setting the s500 frame in QGC it changes the thresholds to much higher values, causing instability?

Thank you very much