ekf2: allow yaw estimator to run when disarmed (if not at rest)

[dagar]

This is to allow yaw estimator to run and potential perform yaw align before the vehicle is armed. Potentially useful for cases like #19393.

PX4-Autopilot/src/modules/ekf2/EKF/gps_control.cpp

Lines 139 to 147 in bc26b73

	} else if (gps_checks_passing && !_control_status.flags.yaw_align && (_params.mag_fusion_type == MAG_FUSE_TYPE_NONE)) {
	// If no mag is used, align using the yaw estimator (if available)
	if (resetYawToEKFGSF()) {
	_information_events.flags.yaw_aligned_to_imu_gps = true;
	ECL_INFO("Yaw aligned using IMU and GPS");
	resetVelocityToGps(_gps_sample_delayed);
	resetHorizontalPositionToGps(_gps_sample_delayed);
	}
	}

[comperem]

hello, this seems to be waiting on something.

it's not clear what, though.

What's the status of this proposed change?

I'm ready to test when it's ready.

[dagar]

hello, this seems to be waiting on something.

it's not clear what, though.

What's the status of this proposed change?

I'm ready to test when it's ready.

@comperem it needs testing. In particular we want to be sure it doesn't fail (yaw estimator converging to something random) if you're not actually moving, but the vehicle_at_rest flag isn't set. For example when there's no airframe selected there's no land detector running and EKF defaults to vehicle_at_rest = false.

[comperem]

hello, this seems to be waiting on something.
it's not clear what, though.
What's the status of this proposed change?
I'm ready to test when it's ready.

@comperem it needs testing. In particular we want to be sure it doesn't fail (yaw estimator converging to something random) if you're not actually moving, but the vehicle_at_rest flag isn't set. For example when there's no airframe selected there's no land detector running and EKF defaults to vehicle_at_rest = false.

Oki doki. I'll give it a try. The yaw is pretty terrible and drifts visibly sitting on the table as it is. I'll provide an update after testing.

[priseborough]

This leaves the yaw estimator vulnerable to GPS errors before flight for air vehicle use and is not safe.

[dagar]

This leaves the yaw estimator vulnerable to GPS errors before flight for air vehicle use and is not safe.

@priseborough I was wondering if we could capture the underlying requirement (eg sufficient lateral acceleration?) rather than relying on the overly broad arm/disarm. People like @comperem are using the system outside of a typical flight controller scenario.

[dagar]

The yaw estimator will now only run if the vehicle is not at rest, GPS velocity is less than EKF2_REQ_SACC, and motion is not excessive (acceleration norm check).