EKF2 consistently blowing up when disabling compass (and being stationary)

ArduPlane Plane 3.5
1

Hi,

I have some questions/concerns about the use of EKF2 while disabling the magnetometers.

We are running AP:Plane 3.5, on 3DR Pixhawks.

If we disable the compass, the EKF consistently blows up after a couple of minutes. A bit of drift in yawing is expected, but it quite quickly starts to spin, and after 1-2 minutes, the roll/pitch also spins up and we get “Bad AHRS”.

By changing to EKF1 (or the old DCM), we don’t see this behaviour.

Is this normal? Image is from ekf2_magoff_bad_10.BIN

ekf2_magoff_bad_instability.png1467×429 11.6 KB

Attached is a couple of logs.
https://dl.dropboxusercontent.com/u/2736420/007%20logs/20160405_5_x8_007m2_ekf2_magoff_bad_5.BIN
https://dl.dropboxusercontent.com/u/2736420/007%20logs/20160405_6_x8_007m2_ekf1_magoff_ok_ekf2running_bad_6.BIN
https://dl.dropboxusercontent.com/u/2736420/007%20logs/20160405_10_x8_007_ekf2_magoff_bad_10.BIN
https://dl.dropboxusercontent.com/u/2736420/007%20logs/20160405_14_x8_007_ekf2_magon_maybeok_14.BIN

I really appreciate all inputs.

Regars,
Kristian

2

Hi Kristian, sorry for not replying earlier.
This is indeed a bug in EKF2 and has caused a couple of crashes. It has been fixed in the 3.5.3 release for plane.
Cheers, Tridge