Energy-efficient, Precise UWB-based 3-D Localization of Sensor Nodes with a Nano-UAV

Smart interaction between autonomous centimeterscale unmanned aerial vehicles (i.e., nano-UAVs) and Internet-of-Things (IoT) sensor nodes is an upcoming high-impact scenario. This work tackles precise 3D localization of indoor edge nodes with an autonomous nano-UAV without prior knowledge of their position. We employ ultrawide-band (UWB) and wake-up radio (WUR) technologies: we perform UWB-based ranging and data exchange between the nano-UAV and the nodes, while the WUR minimizes the sensors’ power consumption. UWB-based precise localization requires addressing multiple sources of error, such as UWB ranging noise and UWB antennas’ uneven radiation pattern. The limited computational resources aboard a nano-UAV further complicate this scenario, requiring real-time execution of the localization algorithm within a microcontroller unit (MCU). We propose a novel UWB-based localization system for nano-UAVs, composed by i) a lightweight localization algorithm, ii) an optimal flight strategy, and iii) a ranging-error correction model. Our 3D flight policy requires only five UWB measurements to feed the localization algorithm, which bounds the localization error within 28 cm, and runs in 1:2 ms on a Cortex-M4 MCU. Localization accuracy is improved by an additional 25to a novel error correction model. Leveraging the WUR, the entire localization/data-exchange cycle costs only 24mJ at the sensor node, which is 50 times more energy efficient than the State-of-the-Art with comparable localization accuracy.