  This paper explores a method of localization and navigation of indoor mobile
robots using a node graph of landmarks that are based on fiducial markers. The
use of ArUco markers and their 2D orientation with respect to the camera of the
robot and the distance to the markers from the camera is used to calculate the
relative position of the robot as well as the relative positions of other
markers. The proposed method combines aspects of beacon-based navigation and
Simultaneous Localization and Mapping based navigation. The implementation of
this method uses a depth camera to obtain the distance to the marker. After
calculating the required orientation of the marker, it relies on odometry
calculations for tracking the position after localization with respect to the
marker. Using the odometry and the relative position of one marker, the robot
is then localized with respect to another marker. The relative positions and
orientation of the two markers are then calculated. The markers are represented
as nodes and the relative distances and orientations are represented as edges
connecting the nodes and a node graph can be generated that represents a map
for the robot. The method was tested on a wheeled humanoid robot with the
objective of having it autonomously navigate to a charging station inside a
room. This objective was successfully achieved and the limitations and future
improvements are briefly discussed.
