Commits on Nov 28, 2024

1. AP_InertialSensor: fixed Q calculation for notch filters …

   when doing the init() we must use the reference frequency, not the
   current frequency. Using the current frequency leaves us with an
   incorrect value for Q. If the current frequency is below the reference
   frequency (which shouldn't happen in 4.5, but has been seen in 4.3)
   then the Q can be much too low and massive phase lag can happen.
   
   The vulnerability in 4.5.x is that the current frequency could be well
   above the reference frequency. For example, the user may be doing a
   motor test at 30s after boot, which is when we stop the
   sensors_converging() test, and thus is the last time we call
   init(). In that case we can end up with a Q which is much larger than
   the one that should come from INS_HNTCH_FREQ and INS_HNTCH_BW, and
   thus end up with a filter that produces a lot less attenuation than is
   desired, potentially leading to instability due to high noise.
   
   There are other scenarios that can cause this - for example a motor
   test of a fwd motor at 30s after boot, or a spurious FFT peak due to
   someone knocking the aircraft, or the vibration of a IC engine.

   

   tridge committed Nov 28, 2024
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2. AP_InertialSensor: make sure notch is still attenuating noise during … …

   …warmup

   

   andyp1per committed Nov 28, 2024
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