PX4/Ardupilot rate controller performance in GPS denied scenarios

[Pallav1299]

Hi

Thanks for sharing this work.

This response brought a few questions regarding PX4/Ardupilot's body rate controller performance in GPS denied environments(like indoors, caves etc).

Questions:

1. From the discussion and core estimator configs in mrs_uav_system, it seems like GPS is the primary source of position corrections in PX4 EKF. Am I right? Are there any secondary or tertiary sources configured in PX4 EKF?
2. AFAIK GPS data is used to estimate the IMU gyro and accel biases. Right? If GPS is denied/degraded(e.g. indoors) and LIO/VIO is the active estimator in EstimationManager, what happens to the body rate controller on PX4/Ardupilot which relies on IMU Gyro/Accel data?
3. How does the PX4 body rate controller cope with the IMU bias drifts? Won't it lead to degrading control performance if not handled?
4. Won't we need external estimator(LIO/VIO etc.) corrections to be sent to PX4/Ardupilot apart from the desired body rates in order to correct the accumulated drifts? Do you foresee any challenges with this?

Could you please clarify?

Thanks again