Perception
ArUco markers (which are a type of fiducial markers) are special patterns than encode numbers:
Often time the course will have these placed around so we can orient our rover and execute a certain task.
We use a modified version of the aruco_detect package to detect AR tags. OpenCV is used to run detection on the camera stream. This gives us information about where the tag is in pixel space, specifically its four corners. We can then fuse this with point cloud data, which gives us the xyz position for any given pixel relative to the camera. Specifically, we query the pointcloud at the center of the marker and thus find its transform relative to the rover.
We then publish the tags to the tf tree.
- AruCo: Special pattern of black and white blocks that encode a number. Often times called a fiducial marker
- OpenCV: A computer vision library
- Point Cloud: A collection of 3D points that roughly describe a scene
- Stereo Camera: A camera that uses stereo rectification to produce point clouds
- Odometry: The "pose" of an object, in other words description of where it is in the world (usually position and rotation)
- Pixel Space (or Camera Space): x and y coordinates of where a pixel is in an image