Home        Store        Docs        Blog

Yaw Drift due to increase of EKF_GYRO_BIAS estimation

I have Pixhawk 2.4.8 otopilot with ArduSub_V3.5. 4 firmware installed on a custom ROV.

The problem (figure below) is that yaw (ATT.Yaw) info displayed on QGroundControl_v3.5.3 switches between EKF primary (NKF1.Yaw) and secondary (NKF6.Yaw) solutions, when the vehicle is stationary. Also, EKF secondary yaw solution (NKF6.Yaw) drifts due to drift in gyro bias estimation (NKF6.GZ).

I have checked that Magnetometers are well calibrated and give correct results.

Although Gyro-Z measurement from first IMU (IMU1.GyrZ) seems stationary, IMU2 (IMU2.GyrZ) seems to be drifting, but I dont thing this is a problem because the values are very small and I dont see and problems in other tests.

When I rotate the vehicle at 90deg intervals, I see that yaw values (NKF1.Yaw and NKF6.Yaw) are drifting even though the vehicle stays stationary. NKF1.GZ and NKF6.GZ values shows huge changes.

I have checked that Magnetometers are well calibrated and give correct results.

Gyro measurements seems fine…

I think the problem is that Gyro.Z bias estimations in EKF do grows too much to make Yaw estimation drifting. Magnetometer and Gyro sensors seems to be measuring correctly. Do you have any suggestions?

Best Wishes.