as2_msgs

The messages, services and actions Aerostack2 defines, and where each one is used.

as2_msgs holds the interface types Aerostack2 adds to the standard ROS 2 ones. Everything else uses std_msgs, geometry_msgs, sensor_msgs and the other common packages. The definitions are in the as2_msgs package.

#include <as2_msgs/msg/platform_info.hpp>
#include <as2_msgs/action/takeoff.hpp>

from as2_msgs.msg import PlatformInfo
from as2_msgs.action import Takeoff

Platform and control

Type	What it carries	Used on
`msg/PlatformInfo`	The platform's connection, arming, offboard, state and control mode	`platform/info`
`msg/PlatformStatus`	A state of the platform state machine	Inside `PlatformInfo`
`msg/PlatformStateMachineEvent`	An event for the platform state machine	Inside `SetPlatformStateMachineEvent`
`msg/ControlMode`	A control mode and a yaw mode	Inside `PlatformInfo`, `ControllerInfo` and `SetControlMode`
`msg/ControllerInfo`	The controller's input and output control modes	`controller/info`
`msg/Thrust`	A collective thrust	`motion_reference/thrust`, `actuator_command/thrust`
`msg/AlertEvent`	An alert, such as a kill switch	`alert_event`
`srv/SetControlMode`	Asks for a control mode	`controller/set_control_mode`, `set_platform_control_mode`
`srv/ListControlModes`	Returns the control modes a platform supports	`platform/list_control_modes`
`srv/SetPlatformStateMachineEvent`	Sends an event and returns the new state	`platform/state_machine_event`
`msg/Acro`	Body rates and a thrust vector	The Gazebo platform's bridge only

PlatformInfo

msg/PlatformInfo.msg

std_msgs/Header header
bool connected
bool armed
bool offboard
as2_msgs/PlatformStatus status
as2_msgs/ControlMode current_control_mode

PlatformStatus and PlatformStateMachineEvent

The two share some names but not their values. LANDED is 1 as a state and 5 as an event.

State	Value	Event	Value
`EMERGENCY`	`-1`	`EMERGENCY`	`-1`
`DISARMED`	`0`	`ARM`	`0`
`LANDED`	`1`	`DISARM`	`1`
`TAKING_OFF`	`2`	`TAKE_OFF`	`2`
`FLYING`	`3`	`TOOK_OFF`	`3`
`LANDING`	`4`	`LAND`	`4`
		`LANDED`	`5`

Aerial platform shows which event leads to which state.

ControlMode

msg/ControlMode.msg

std_msgs/Header header

int8 NONE      = 0
int8 YAW_ANGLE = 1  # rad
int8 YAW_SPEED = 2  # rad/s
int8 yaw_mode

int8 UNSET            = 0
int8 HOVER            = 1
int8 POSITION         = 2  # x, y, z
int8 SPEED            = 3  # vx, vy, vz
int8 SPEED_IN_A_PLANE = 4  # vx, vy, z
int8 ATTITUDE         = 5  # roll, pitch, yaw
int8 BODY_RATES       = 6  # collective thrust and p, q, r
int8 TRAJECTORY       = 7  # x, y, z, vx, vy, vz, ax, ay, az
int8 control_mode

ListControlModes doesn't return ControlMode messages. It packs each mode into one byte, with other numbers than the message, and the control modes files of the platforms and controller plugins use the same bytes.

Bits	Holds	Values
7 to 4	The control mode	Unset `0`, hover `1`, body rates `2`, attitude `3`, speed `4`, speed in a plane `5`, position `6`, trajectory `7`
3 to 2	The yaw mode	Angle `0`, speed `1`, none `2`
1 to 0	Nothing	Ignored

So 0b01000100 is speed with a yaw speed. as2_core/utils/control_mode_utils.hpp converts between the two forms.

AlertEvent

msg/AlertEvent.msg

int8 KILL_SWITCH     = -1
int8 EMERGENCY_HOVER = -2
int8 EMERGENCY_LAND  = -3
int8 INFO_ALERT      = 0
int8 FORCE_HOVER     = 1
int8 FORCE_LAND      = 2
int8 alert
string description

Negative alerts are meant for the platform and positive ones for the rest of the stack. Only the kill switch and the emergency hover are acted on today, as Alerts explains.

References and trajectories

Type	What it carries	Used on
`msg/TrajectoryPoint`	One point of a trajectory, with its position, velocity, acceleration and yaw	Inside `TrajectorySetpoints`
`msg/TrajectorySetpoints`	The points of a trajectory, all in the header's frame	`motion_reference/trajectory`, `actuator_command/trajectory`
`msg/YawMode`	How a behavior handles the yaw	The goals of the motion and path planning behaviors
`msg/PoseWithID`	A pose with a name	The follow path and swarm goals
`msg/PoseStampedWithID`	A stamped pose with a name	The trajectory generation goal
`msg/PoseStampedWithIDArray`	A list of named poses	`motion_reference/modify_waypoint`
`msg/PoseWithIDArray`	A list of named poses	The swarm's `dynamic_swarm_formation`

msg/TrajectoryPoint.msg

string id
geometry_msgs/Vector3 position
geometry_msgs/Vector3 twist         # A linear velocity, despite its name
geometry_msgs/Vector3 acceleration
float32 yaw_angle                   # rad

YawMode

Mode	Value	The drone faces
`KEEP_YAW`	`0`	Where it faces now
`PATH_FACING`	`1`	Along the path
`FIXED_YAW`	`2`	The direction in `angle`, in radians
`YAW_FROM_TOPIC`	`3`	The yaw given on a topic
`YAW_FROM_ORIENTATION`	`4`	The orientation of the pose. No behavior supports it yet
`YAW_TO_FRAME`	`5`	The frame the goal is given in
`FACE_REFERENCE`	`6`	The next reference

Not every behavior takes every mode. The go to behavior takes the first four, for example, and only the trajectory generator takes FACE_REFERENCE.

Behaviors

msg/BehaviorStatus is the state every behavior publishes on <behavior>/_behavior/behavior_status, which is IDLE, RUNNING or PAUSED. Behaviors lists the rest of their interfaces.

Actions

Action	Goal	Result	Feedback
`Takeoff`	`takeoff_height` in m, `takeoff_speed` in m/s	`takeoff_success`	`actual_takeoff_height`, `actual_takeoff_speed`
`Land`	`land_speed` in m/s	`land_success`	`actual_land_height`, `actual_land_speed`
`GoToWaypoint`	`target_pose` as a `PointStamped`, `max_speed`, `yaw`	`go_to_success`	`actual_speed`, `actual_distance_to_goal`
`FollowPath`	`header` with the path's frame, `path` as `PoseWithID[]`, `max_speed`, `yaw`	`follow_path_success`	`actual_speed`, `actual_distance_to_next_waypoint`, `remaining_waypoints`, `next_waypoint_id`
`FollowReference`	`target_pose` as a `PointStamped`, `max_speed_x`, `max_speed_y`, `max_speed_z`, `yaw`	`follow_reference_success`	`actual_speed`, `actual_distance_to_goal`
`GeneratePolynomialTrajectory`	`stamp`, `path` as `PoseStampedWithID[]`, `max_speed`, `yaw`, `start_on_paused`, `follow_reference_mode`	`trajectory_generator_success`	`next_waypoint_id`, `remaining_waypoints`
`NavigateToPoint`	`point` as a `PointStamped`, `navigation_speed`, `yaw`	`success`	`current_pose`, `current_speed`, `navigation_time`, `estimated_time_remaining`, `distance_remaining`
`SetArmingState`	`request`	`success`	None
`SetOffboardMode`	`request`	`success`	None
`DetectObjects`	`threshold`, `target_classes`	`perceptions`	`perceptions`
`PointGimbal`	`control` as a `GimbalControl`, `follow_mode`, `mode`	`success`	`gimbal_attitude`, `gimbal_speed`
`GripperHandler`	`request_gripper`, `true` to close	`gripper_success`	`state_gripper`
`MassEstimation`	`request`	`success`	None
`ForceEstimation`	`request`	`success`	None
`SwarmFlocking`	`virtual_centroid`, `swarm_formation` as `PoseWithID[]`, `drones_namespace`	`swarm_success`	`swarm_pose`

start_on_paused generates the trajectory and leaves the behavior paused until it's resumed. follow_reference_mode takes a single waypoint and keeps tracking it after the trajectory ends.

The point gimbal behavior only takes GimbalControl in position mode, without follow_mode.

Perception

Type	What it carries	Used on
`msg/ObjectPerception`	One detection, with its class, image box, keypoints and an optional 3D pose	Inside `ObjectPerceptionArray`
`msg/ObjectPerceptionArray`	The detections of one image	`detections_data`, and the `DetectObjects` result and feedback
`msg/GimbalControl`	A gimbal command, as angles or rates	`platform/<gimbal>/gimbal_command`
`msg/UInt16MultiArrayStamped`	A list of numbers with a timestamp	The simple EKF's internal debug topics

In ObjectPerception, pose_valid says whether the hypothesis carries a 3D pose or only an image position.

Missions

Type	What it carries	Used on
`msg/MissionUpdate`	A command for the mission executor, with the mission as JSON	`/mission_update`

Mission executor lists the commands it handles.

GPS, geozones and TF

Type	What it does	Used on
`srv/SetOrigin`	Sets the GPS origin	`set_origin`
`srv/GetOrigin`	Returns the GPS origin	`get_origin`
`msg/Geozone`	A geofence or geocage, its height limits and the alert it raises	Inside `SetGeozone` and `GetGeozone`
`srv/SetGeozone`	Adds a geozone	`geozones/set_geozone`
`srv/GetGeozone`	Lists the geozones	`geozones/get_geozone`
`msg/PolygonList`	The geozones as polygons, for RViz	`geozones_rviz`
`srv/AddStaticTransform`	Adds a static transform	`external_object_to_tf/add_static_transform`
`srv/AddStaticTransformGps`	Adds a static transform from a GPS position	`external_object_to_tf/add_static_transform_gps`

Not used yet

These types are defined but nothing in Aerostack2 serves or publishes them, so don't build on them.

Kind	Types
Messages	`FollowTargetInfo`, `MissionEvent`, `NodeStatus`, `Speed`, `TrajGenInfo`
Services	`DynamicFollower`, `DynamicLand`, `GeopathToPath`, `ModifySwarm`, `PackagePickUp`, `PackageUnPick`, `PathToGeopath`, `SetSpeed`
Actions	`DetectArucoMarkers`. The object perception behavior detects ArUco markers through `DetectObjects`

The GPS behavior tree nodes call a geopath_to_path service, but no node serves it, so they wait for it forever.

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