Stops vertical velocity bias errors preventing the vehicle from landing.
Use of the vertical derivative is blended in so that for zero vertical velocity set point, the local_position.vz is used and when the magnitude of the vertical velocity setpoint exceeds the landing speed, the local_position.z_deriv is used.
Using the vertical derivative estimate prevents vertical velocity offsets caused by estimation vertical velocity errors preventing the vehicle disarming.
When the EKF is not fusing in observations from the NE global reference frame, the tolerance to yaw errors is much higher. This changes will prevent false triggering of the preflight fail check when operating indoors without GPS where mag field errors can be high.
Before that, different modules (ekf2, commander & land detector) changed
params upon different events:
- ekf2 & commander set params after disarm
- land detector set params on land detected
If the 2 events were several 100ms appart, it led to 2 param saves, and
the latter param set could have been blocked by an ongoing save. And if
the land detector was blocked, it could lead to mag timeouts.
This patch makes all modules use the same event, thus only a single param
save will happen.
If we want to have guarantees to never block, we should introduce a
param_try_set() API method.
_should_stop_file_log is set after disarming: logging continues for 1s
to measure the CPU usage.
During that time, other modules might change params (such as ekf), and
we don't need to have these the log. However currently all modules do
not notify the system when setting params after disarming.
Meaning this patch is not strictly needed, it's more a preventive
measure.
This check is performed for up to 30 seconds after takeoff or until a horizontal speed of 5 m/s has been achieved.
If the vehicle is not landed and the check is active, then the yaw will be declared as failed if the velocity innovations fail for a continuous period of 1 second.
This will cause the local and global position and velocity validity to be latched false to prevent unsafe use of position control modes.
Daniel Agar