An Ultra-Wideband Localization Approach for Unknown Anchor Distributions

Precise localization of mobile robots is key to many (semi)-autonomous operations, such as planetary exploration. In situations, where Global Navigation Satellite Systems (GNSS) is unavailable, Ultra-Wideband (UWB) technology is a common replacement. This typically relies on the positions of distributed anchors to be known beforehand. In this work we expand on a system, that remotely distributes the anchors, which means the position of them is unknown. The robot is equipped with three UWB tags, which perform Two-Way-Ranging (TWR) distance measurements with all the anchors. These distances are used to determine the relative position of the anchors to the robot. These positions are interpreted as landmarks in an Extended Kalman Filter (EKF)-Simultaneous Localization and Mapping (SLAM) algorithm, which combines them with the wheel odometry of the robot. Our experiments show promising results in a setup with four anchors, performing considerably better than the wheel odometry on its own. The system is also capable of operating through an outage of the UWB anchors. After such an outage the pose of the robot is corrected in multiple experiments, though not to the same standard as before the outage.