Bluetooth Low Energy based Technology for Small UAS Indoor Positioning

Unmanned Aircraft Systems (UASs) or Remotely Piloted Aircraft Systems (RPASs), commonly known as drones, constitute a research field that has been extensively explored in the last decade, in operational contexts such as search and rescue, disaster assessment, urban traffic monitoring, logistics, or in military operations like surveillance into war zone, reconnaissance, and many more. In the framework of autonomous UAV missions, precise feedback on real-time aircraft position is very important. For outdoor operations, conventional positioning methods are based on GNSS (Global Navigation Satellite System) and/or IMU (Inertial Measurement Unit) sensors. There are different technologies alternative to GNSS-based approaches for UAV positioning in indoor navigation. They are based on onboard sensor integration, e.g., camera, radar, sonar, LiDAR, Inertial Navigation System (INS), Ultra-Wide Band (UWB) devices. In this paper we propose, as a preliminary stage, a low-cost Indoor Positioning System (IPS) for UAVs, based on Bluetooth Low Energy (BLE) beacons, by exploiting the RSSI (Radio Signal Strength Indicator). BLE is a low power consumption technology aimed at transmitting small amounts of data. A mathematical model is established to analyze the relation between the RSSI and the distance from two or three Bluetooth devices, an onboard receiver (Arduino Nano 33 BLE, used as Single-Board Computer (SBC)) and transmitters positioned in the indoor operating field (BLE beacons). Position estimation is achieved by trilateration, and 1-D Kalman filtering is applied to correct data from noise, drift, and bias errors. Experimental results and system performance analysis show the feasibility of this methodology. Future developments will involve outdoor tests for a safe landing area determination system developed by the authors.