ReLoki: Infrastructure-free Distributed Relative Localization using On-board UWB Antenna Arrays

Coordination of multi-robot systems require some form of localization between agents, but most methods today rely on some external infrastructure. Ultra Wide Band (UWB) sensing has gained popularity in relative localization applications, and we see many implementations that use cooperative agents augmenting UWB range measurements with other sensing modalities (e.g., ViO, IMU, VSLAM) for infrastructure-free relative localization. A lesser researched option is using Angle of Arrival (AoA) readings obtained from UWB Antenna pairs to perform relative localization. In this paper we present a UWB platform called ReLoki that can be used for ranging and AoA-based relative localization in~3D. ReLoki enables any message sent from a transmitting agent to be localized by using a Regular Tetrahedral Antenna Array (RTA). As a full scale proof of concept, we deploy ReLoki on a 3-robot system and compare its performance in terms of accuracy and speed with prior methods.