This is a first baseline implementation for collision avoidance with aircraft equipped with transponders. Since the drone-to-drone and drone-to-airplane system will be regulated by a standard, we do carefully avoid to do anything too fancy. This implementation allows to reduce altitude to get close to ground and land immediately or RTL. This is similar to what a human pilot would do and allows to get out of manned airspace which is at higher altitudes.
The function `mission_item_to_position_setpoint()` is called in
`FollowTarget::update_position_sp()`. The nav_cmd is a
NAV_CMD_DO_FOLLOW_REPOSITION as set earlier in `set_follow_target_item`.
Since `mission_item_to_position_setpointi` returns early because the item
presumably contains no position, the lat/lon of the mission_item are
not copied over to the position_setpoint and therefore the vehicle will
never move in follow me position mode.
When checking a mission, the takeoff altitude is being checked
against the waypoint acceptance radius to ensure the MAV being
clear from ground before heading to the next waypoint.
However, until now the _horizontal_ acceptance radius was being
used, instead of the altitude reference value.
Targets PX4/Firmware/#7379
Instead of just checking whether the first waypoint is too far away from
home it makes sense to also check between waypoints.
This can prevent
- flyaways due to user errors, or
- catch the corner case where a takeoff waypoint is added to a mission
and therefore the first waypoint is not too far away, however, the
subsequent waypoints are still too far away.
This change limits all mission items to the maximum flight altitude. The mission will still be executed and flown,
but the vehicle will never exceed the mission altitude. This ensures the vehicle can always reach the mission
items. Wether or not the entire mission should be rejected if it falls outside of the fenced area is enforced
in the mission feasibility checker function.
This allows to run a command / function once when being deactivated. This avoids having flight modes which are not active run unnecessary code all the time.
This will initialize those structs with zero in all fields not set
and all fields set will only be change once to the final value not
wasting CPU time zeroing it.
This will guarantee that no non-unitialized structs will have
a trash value on from_external causing it to be sent to the
MAVLink channel without need it.
- avoids race conditions when geofence data is updated in flight. During
a transfer, the geofence module will not check for violations, which
is done with the new dm_trylock method.
- there is an update counter stored in dataman, and for each write
transaction this is increased, so that the geofence module can reload
the data upon data change (after it's unlocked).
- single dm item updates are atomic already, so resetting the polygons
to 0 does not need locking.
Daniel Agar