3.6 KiB
Map-based navigation with ArUco markers
Info Marker detection requires the camera module to be correctly plugged in and configured.
Hint We recommend using our custom PX4 firmware.
aruco_map module detects whole ArUco-based maps. Map-based navigation is possible using vision position estimate (VPE).
Configuration
In order to enable map detection set aruco_map and aruco_detect arguments to true in ~/catkin_ws/src/clever/clever/launch/aruco.launch:
<arg name="aruco_detect" default="true"/>
<arg name="aruco_map" default="true"/>
Set aruco_vpe to true to publish detected camera position to the flight controller as VPE data:
<arg name="aruco_vpe" default="true"/>
Marker map definition
Map is defined in a text file; each line has the following format:
marker_id marker_size x y z z_angle y_angle x_angle
N_angle is the angle of rotation along the N axis in radians.
Map path is defined in the map parameter:
<param name="map" value="$(find aruco_pose)/map/map.txt"/>
Some map examples are provided in ~/catkin_ws/src/clever/aruco_pose/map.
Grid maps may be generated using the genmap.py script:
rosrun aruco_pose genmap.py length x y dist_x dist_y first > ~/catkin_ws/src/clever/aruco_pose/map/test_map.txt
length is the size of each marker, x is the marker count along the x axis, y is the marker count along the y axis, dist_x is the distance between the centers of adjacent markers along the x axis, dist_y is the distance between the centers of the y axis, first is the ID of the first marker (bottom left marker, unless --top-left is specified), test_map.txt is the name of the generated map file. The optional --top-left parameter changes the numbering of markers, making the top left marker the first one.
Usage example:
rosrun aruco_pose genmap.py 0.33 2 4 1 1 0 > ~/catkin_ws/src/clever/aruco_pose/map/test_map.txt
Checking the map
The currently active map is posted in the /aruco_map/image ROS topic. It can be viewed using web_video_server by opening the following link: http://192.168.11.1:8080/snapshot?topic=/aruco_map/image
Current estimated pose (relative to the detected map) is published in the aruco_map/pose ROS topic. If the VPE is disabled, the aruco_map TF frame is created; otherwise, the aruco_map_detected frame is created instead. Visualization for the current map is also posted in the aruco_map/visualization ROS topic; it may be visualized in rviz.
An easy to understand detected map visualization is posted in the aruco_map/debug ROS topic (live view is available on http://192.168.11.1:8080/stream_viewer?topic=/aruco_map/debug):
Coordinate system
The marker map adheres to the ROS coordinate system convention, using the ENU coordinate system:
- the x axis points to the right side of the map;
- the y axis points to the top side of the map;
- the z axis points outwards from the plane of the marker
VPE setup
In order to enable vision position estimation you should use the following PX4 parameters.