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Nodes

fiducial_slam

fiducial_slam receives fiducial_poses from aruco_detect and combines them to build a map of fiducial locations and an estimate of the robot's pose.

Subscribed Topics

/fiducial_transforms (fiducial_msgs/FiducialTransform)

• Poses of observed fiducials.

/tf (tf/tfMessage)

• Transforms.

Published Topics

/fiducial_pose (geometry_msgs/PoseWithCovarianceStamped)

• Robot's estimated pose in the map, with covariance.

fiducials (visualization_msgs/Marker)

• Markers showing the map, for use with rviz for diagnostics.

/fiducial_map (fiducial_msgs/FiducialMapEntryArray)

• The current state of the map.

/tf (tf/tfMessage)

• Transforms.

Services

~clear_map (std_srvs/Empty)

• Clears the map and enables auto-initialization.

Parameters

~map_file (string, default: map.txt)

• Path to the file containing the generated map.

~odom_frame (string, default: not set)

• If this is set to a non-empty string, then the result of the localization is published as a correction to odometry. For example, the odometry publishes the tf from map to odom, and this node publishes the tf from odom to base_link, with the tf from map to odom removed.

~map_frame (string, default: map)

• The name of the map (world) frame.

~base_frame (string, default: base_link)

• The child frame of the tf we publish.

~future_date_transforms (double, default: 0.1)

• Time with which to post-date the transform that is published, to indicate that this transform is valid into the future.

~publish_6dof_pose (bool, default: false)

• If true, unmodified poses are published, otherwise they are constrained to have zero z translation and only the yaw component of rotation.

~read_only_map (bool, default: false)

• if true, the map is not modified, and only localization is performed.

~tf_publish_interval (float, default: 1.0)

• Specifies an interval at which poses are published, even if no fiducials are observed. This is useful in cases where the fiducial pose is used as a correction to odometry.

File Formats

The map file is a text file with a line for each fiducial id: `

id x y z pan tilt roll variance numObservations links

x, y and z specify the translation of the fiducial from the origin in meters, and pan, tilt, and roll specify its orientation in degrees. The fields variance and numObservations represent how good the pose estimate is considered to be, and how many observations were used to generate it. links is a list of the ids of fiducials that have been observed at the same time as the current fiducial. The coordinate frame used is the map frame, which is relative to the floor, so markers of the ceiling will have been rotated. The supplied launch files specify the map file as ~/.ros/slam/map.txt.