Fix mag offset correction from estimated bias #21812
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| @@ -110,7 +110,7 @@ void Magnetometer::SensorCorrectionsUpdate(bool force) | |||
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| bool Magnetometer::set_offset(const Vector3f &offset) | |||
| { | |||
| if (Vector3f(_offset - offset).longerThan(0.01f)) { | |||
| if (Vector3f(_offset - offset).longerThan(0.001f)) { | |||
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This was done to minimize writing out the parameters after every flight for negligible changes.
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Ok, I can revert this if you're fine with changing magb_vref (as modified in this PR). Otherwise the change is so small that even an offset of 0.1gs is never getting corrected (the change in offset is ~0.003gs in sim)
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Let's set it to 0.005 so it gets applied if the change in offset is > 1% of the usual mag field
| @@ -329,7 +329,7 @@ void VehicleMagnetometer::UpdateMagCalibration() | |||
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| if (_calibration[mag_index].set_offset(mag_cal_offset)) { | |||
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| PX4_INFO("%d (%" PRIu32 ") EST:%d offset: [%.2f, %.2f, %.2f]->[%.2f, %.2f, %.2f] (full [%.3f, %.3f, %.3f])", | |||
| PX4_INFO("%d (%" PRIu32 ") EST:%d offset: [%.3f, %.3f, %.3f]->[%.3f, %.3f, %.3f] (full [%.3f, %.3f, %.3f])", | |||
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Some of these strings weren't being fully captured, maybe check a quick example.
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| if (cal.total_time_us > 30_s) { | ||
| if (cal.total_time_us > 10_s) { |
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Note this magic number will also apply for accel and gyro.
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Yes, I don't think it's a problem for those either.
- since last_us is set to 0 every time the bias is not observable, the total time was also reset -> needed 30 consecutive seconds in mag 3D to be declared "stable" - after landing, the mag_aligned_in_flight flag is reset. Using this for bias validity makes it invalid before we have a chance to save it to the calibration.
For the mag, 30s of bias learning is a lot, given that it is only active during turns and that it usually converges in < 5 seconds
in air bias estimation is usually really accurate and should be weighted more heavily compared to the calibration parameters that are often more approximate given the worse magnetic environment near the ground.
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This pull request has been mentioned on Discussion Forum for PX4, Pixhawk, QGroundControl, MAVSDK, MAVLink. There might be relevant details there: https://discuss.px4.io/t/px4-maintainers-call-july-11-2023/33057/1 |
Solved Problem
I realized that the estimated mag bias was never applied back to the calibration. I found the following bugs:
set_offsetSolution
Fix 1.; now it's truly a period of accumulated time, no need to be consecutive anymore
Remove check for mag_aligned_in_flight; we anyway don't enter mag 3D before that
Reduce the minimum mag offset param change to 0.001gs
Additionally:
Reduce the required stability period to 10s. For the mag, 30s of bias learning is a lot, given that it is only active during turns and that it usually converges in < 5 seconds (and we start counting after convergence)
Increase uncertainty of calibration parameters: in air bias estimation is usually really accurate and should be weighted more heavily compared to the calibration parameters that are often more approximate given the worse magnetic environment near the ground.
Changelog Entry
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