Aerial platform

Every platform is built on as2::AerialPlatform, so they all offer the interfaces on this page. The node is called platform. Aerial platform explains what the platform does with them.

Topics

Topic	Direction	Type	QoS
`platform/info`	Publishes	`as2_msgs/PlatformInfo`	Reliable
`actuator_command/pose`	Subscribes	`geometry_msgs/PoseStamped`	Sensor data
`actuator_command/twist`	Subscribes	`geometry_msgs/TwistStamped`	Sensor data
`actuator_command/thrust`	Subscribes	`as2_msgs/Thrust`	Sensor data
`actuator_command/trajectory`	Subscribes	`as2_msgs/TrajectorySetpoints`	Sensor data
`alert_event`	Subscribes	`as2_msgs/AlertEvent`	Reliable

platform/info is published at info_freq, 10 Hz by default. It says whether the drone is connected, armed and in offboard, where the state machine is, and which control mode is active.

The actuator commands come from the motion controller. The platform sends the latest ones to the drone at cmd_freq, 100 Hz by default, once a control mode is set and the drone is connected, armed and in offboard. It reads TF to convert them into the frames the control mode asks for.

alert_event acts on two alerts. A kill switch cuts the motors and an emergency hover stops the drone, and both put the state machine in its emergency state. Every other alert is ignored.

Services

Service	Type	What it does
`set_arming_state`	`std_srvs/SetBool`	Arms with `true` and disarms with `false`
`set_offboard_mode`	`std_srvs/SetBool`	Turns offboard on with `true` and off with `false`
`set_platform_control_mode`	`as2_msgs/SetControlMode`	Switches the control mode. Fails if the platform doesn't support it
`platform_takeoff`	`std_srvs/SetBool`	Takes off natively. The request's value is ignored
`platform_land`	`std_srvs/SetBool`	Lands natively. The request's value is ignored
`platform/list_control_modes`	`as2_msgs/ListControlModes`	Returns the control modes the platform supports
`platform/state_machine_event`	`as2_msgs/SetPlatformStateMachineEvent`	Sends an event to the state machine and returns the new state

Most services sit at the root of the namespace

The first five services aren't under platform/. For drone0 they're /drone0/set_arming_state, /drone0/platform_takeoff and so on. Only the last two are under platform/.

platform_takeoff and platform_land move the state machine on from taking off to flying, and from landing to landed. They don't start a take-off or a landing in the state machine, so send the TAKE_OFF or LAND event to platform/state_machine_event first. The take-off and land behaviors do this for you.

platform/state_machine_event is named after the node, unlike the other services. If you launch the platform under another node name the service moves with it, and the take-off and land behaviors can no longer find it.

Sensors

Platforms publish their sensors with the helpers in as2_core/sensor.hpp, which put each one under sensor_measurements/. Which sensors there are depends on the drone, so each platform's page lists its own. These are the usual ones.

Topic	Type	QoS
`sensor_measurements/odom`	`nav_msgs/Odometry`	Sensor data
`sensor_measurements/imu`	`sensor_msgs/Imu`	Sensor data
`sensor_measurements/gps`	`sensor_msgs/NavSatFix`	Sensor data
`sensor_measurements/battery`	`sensor_msgs/BatteryState`	Sensor data
`sensor_measurements/<camera>/image`	`sensor_msgs/Image`	Reliable
`sensor_measurements/<camera>/camera_info`	`sensor_msgs/CameraInfo`	Reliable
`ground_truth/pose`	`geometry_msgs/PoseStamped`	Sensor data
`ground_truth/twist`	`geometry_msgs/TwistStamped`	Sensor data

Cameras go through image_transport, so compressed versions such as sensor_measurements/<camera>/image/compressed appear when their plugins are installed. A camera's topics only appear once its first frame arrives. Each camera also publishes a static transform from base_link to its own frame.

Simulators and motion capture systems publish the ground truth topics, which carry the true pose and velocity of the drone.

Gazebo bridges its sensors instead of using the helpers, so their names differ. A camera publishes sensor_measurements/<camera>/image_raw and a lidar sensor_measurements/<lidar>/scan, named after the sensor in the drone's model. Gazebo has the details.

Parameters

Parameter	Default	What it does
`control_modes_file`		The YAML file that lists the control modes the platform supports. Required
`cmd_freq`	`100.0`	How often commands are sent to the drone, in Hz
`info_freq`	`10.0`	How often `platform/info` is published, in Hz
`tf_timeout_threshold`	`0.05`	How long to wait for a transform, in seconds

Topics

Services

Sensors

Parameters

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