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EKF: tilt_align and uncertainty at high pitch angles #571

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CarlOlsson opened this issue Feb 6, 2019 · 3 comments
Open

EKF: tilt_align and uncertainty at high pitch angles #571

CarlOlsson opened this issue Feb 6, 2019 · 3 comments
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ekf move to PX4-Autopilot potential bug Used for defects in the code that have the potential to create unwanted behaviour

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@CarlOlsson
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CarlOlsson commented Feb 6, 2019

We declare tilt_align = true when the roll + pitch uncertainty is lower than 3 degrees.
https://github.com/PX4/ecl/blob/c52f4bab1a1655f298778b9a815bbe3c70d91529/EKF/control.cpp#L61-L62

This does not work properly at high pitch angles in the same way as the increase in yaw uncertainty at a heading reset wasn't working before.

E.g. for a tailsitter which is booted up with the body x axis facing upwards the tilt_aligned flag is set to true when the pitch and yaw uncertainty is below 3 degrees.

Sidenote:
Currently yaw_align is set to true in initialiseFilter() before tilt_align is set to true in controlFusionModes().
This leads to the fact that the magnetometer is fused before tilt_align is true

@dagar dagar added the ekf label Feb 6, 2019
@priseborough
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@CarlOlsson I think this has been fixed by #549, #552 and #556

@CarlOlsson
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No, the issue is still there.

This makes an assumption that the vehicles z axis is pointing down
https://github.com/PX4/ecl/blob/f95cd4b3584d029c35b288a39180ddf25b2dd004/EKF/control.cpp#L56-L59

@priseborough priseborough added the potential bug Used for defects in the code that have the potential to create unwanted behaviour label Jun 3, 2019
@bresch bresch changed the title EKF: tilt_align and uncertainty at high pitch angels EKF: tilt_align and uncertainty at high pitch angles Jun 25, 2020
@priseborough
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We could use the component of the angle_err_var_vec vector perpendicular to the earth frame D axis to determine of the tilt has aligned.

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Labels
ekf move to PX4-Autopilot potential bug Used for defects in the code that have the potential to create unwanted behaviour
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