A novel artificial landmark for monocular global visual localization of indoor robots

To obtain the pose of a monocular camera installed on the robot relative to the static artificial landmarks in a prepared room is one of many good methods for indoor robot localization. However, the point correspondence problem caused by rotation of cameras and the point detection precision problem are not paid enough attention to. In this paper, we proposed a novel coplanar landmark and a method to calculate the camera pose. The landmark is composed of two carefully placed polygons to contain point correspondence information. In this way, the camera can rotate arbitrarily relative to the landmark. What's more, there are many parallel line pairs and perpendicular line pairs to impose more constraints on the camera pose. In our method, the SUSAN detector is used for edge detection. The line segments of the two polygons are then detected by RANSAC algorithm. After sorting the lines, the corners of each polygon are extracted by intersection of neighboring lines instead of detecting corners directly to improve precision. Once the intrinsic camera parameters and the coordinates of line segments and corners in the world frame and the image frame are derived, the camera pose can be obtained easily from the homography between the world frame and the image frame. Through the analysis of the experimental data, it can be concluded that the robustness and accuracy are much improved, and the rate is high enough for real-time indoor robot localization.