Mission Mode (VTOL)
Mission mode causes the vehicle to execute a predefined autonomous mission (flight plan) that has been uploaded to the flight controller. The mission is typically created and uploaded with a Ground Control Station (GCS) application like QGroundControl (QGC).
VTOL vehicles follow the behavior and parameters of fixed-wing when in FW mode, and of multicopter when in MC mode. For more information see the specific docs for each mode:
The following sections outline mission mode behaviour that is VTOL specificL.
Mission Commands
The following VTOL-specific commands are as defined in the MAVLink specification.
- MAV_CMD_NAV_VTOL_TAKEOFF
MAV_CMD_NAV_VTOL_TAKEOFF.param2(transition heading) is ignored. Instead the heading to the next waypoint is used for the transition heading.
- MAV_CMD_NAV_VTOL_LAND
- MAV_CMD_DO_VTOL_TRANSITION
Otherwise PX4 generally "accepts" the mission commands for fixed wing or multicopter when in the respective modes.
In fixed-wing mode there are the following exceptions:
- MAV_CMD_NAV_LAND is transformed into MAV_CMD_NAV_VTOL_LAND unless NAV_FORCE_VT is set to
0(disabled). - MAV_CMD_NAV_TAKEOFF is not supported.
Mission Command Timeouts
Some mission commands/items can take time to complete, such as a gripper opening and closing, a winch extending or retracting, or a gimbal moving to point at a region of interest.
Where provided PX4 may use sensor feedback from the hardware to determine when the action has completed and then move to the next mission item. If not provided, or if the feedback is lost, a mission command timeout can be used to ensure that these kinds of actions will progress to the next mission item rather than blocking progression.
The timeout is set using the MIS_COMMAND_TOUT parameter. This should be set to be a small amount greater than the time required for the longest long-running action in the mission to complete.
Mission Takeoff
Plan a VTOL mission takeoff by adding a VTOL Takeoff mission item to the map.
During mission execution the vehicle will ascend vertically to the minimum takeoff altitude defined in the MIS_TAKEOFF_ALT parameter, then transition to fixed-wing mode with the heading defined in the mission item. After transitioning the vehicle heads towards the 3D position defined in the mission item.
A VTOL mission requires a VTOL Takeoff mission item (MAV_CMD_NAV_VTOL_TAKEOFF) to takeoff (or a MAV_CMD_NAV_TAKEOFF when the vehicle is in MC mode); if however the vehicle is already flying when the mission is started the takeoff item will be treated as a normal waypoint.