Fast Mutual Relative Localization of UAVs using Ultraviolet LED Markers

Abstract

This paper proposes a new methodology for outdoor mutual relative localization of UAVs equipped with active ultraviolet markers and a suitable camera with specialized bandpass filters. Mutual relative localization is a crucial tool for formation preservation, swarming and cooperative task completion in scenarios in which UAVs share working space in small relative distances. In most current systems of compact UAV swarms the localization of particular UAVs is based on the data obtained from motion capture systems for indoor experiments or on precise RTK-GNSS data outdoor. Such an external infrastructure is unavailable in most of real multi-UAV applications and often cannot be pre-installed. To account for such situations, as well as to make the system more autonomous, reliance on onboard sensors only is desirable. In the proposed approach, we rely on ultraviolet LED markers, that emit light in frequencies that are less common in nature than the visible light or infrared radiation, especially in high intensities. Additionally, common camera sensors are sensitive to ultraviolet light, making the addition of a filter the only necessary modification, keeping the platform low-cost, which is one of the key requirements on swarm systems. This also allows for a smaller size of the markers to be sufficient, without burdening the processing resources. Thus the proposed system aspires to be an enabling technology for deployment of large swarms of possibly micro-scale aerial vehicles in real world conditions and without any dependency on an external infrastructure.

Mutual Localization of UAVs based on Blinking Ultraviolet Markers and 3D Time-Position Hough Transform

“…Our solution extends our previous research on a novel, vision-based mutual localization in the Ultra-Violet (UV) spectrum [17] . Motivated by the low amount of near-UV radiation in sunlight and most artificial sources, compared to the visible spectrum.…”

“…For the sake of brevity, only key properties for our approach are presented, more details are presented in [17].…”

“…This can be leveraged using affordable near-UV LEDs and suitable band-pass filters applied on a monochromatic camera. Tests have shown that the UV radiation refracted through the atmosphere and reflected from matte surfaces can be neglected, see [17]. Artificial radiation sources with strong UV emissions are rare, making this wavelength range very attractive for our application.…”

IMU/Magnetometer/Barometer/Mass-Flow Sensor Integrated Indoor Quadrotor UAV Localization with Robust Velocity Updates

“…Decentralized information filter 3 m * 2 m Decimeter level [12] Optical flow sensor, IMU EKF 6 m * 6 m 0.3 m in mean [13] Ultraviolet LED makers Mutual relative localization 10 m distance Meter level [14] 3D lidar, UWB, IMU EKF Simulation Decimeter level [15] 2D lidar CNN 4 m * 4 m Decimeter level [16] 2D lidar, IMU SLAM 8 m * 8 m 1.0 m for 26 s, 0.5 m for 10 s [17] 2D lidar, IMU Tightly coupled SLAM 60 m corridor Meter level [18] 1D laser, IMU, barometer EKF 5 m * 9 m 0.1 m height accuracy in mean [19] Radar Radar odometry 80 m * 10 m 3.3 m in mean [20] Radar, UWB, IMU EKF 40 m * 40 m 0.8 m in RMS [21] UWB Multilateration 20 m * 30 m, 4 AP 2.0 m in mean [22] UWB TDoA 4 m * 2 m, 4 AP 0.1 m in 75 % [23] UWB, IMU Tightly coupled EKF 19 m * 13 m 0.15 m in mean [24] UWB, monocular camera SLAM 8 m * 8 m 0.23 m in 75 % [25] UWB, RGB-D camera Monte Carlo localization 15 m * 15 m 0.2 m in RMS [26] Ultrasonic Multilateration 4 m * 3 m, 6 AP 0.16 m in RMS [27] Ultrasonic CNN 10 m * 4 m Decimeter level [28] Ultrasonic, time-of-flight camera Multilateration 0.7 m * 0.7 m, 5 AP 0.17 m in median [29] WiFi Fingerprinting 36 m * 17 m, 10 APs 1.7 m in mean [30] WiFi A quasi-taut tether Angle and range-based 2.5 m * 2.5 m 0.37 m in mean * SLAM-simultaneous localization and mapping; 1D/2D/3D-one/two/three-dimensional; EKF-extended Kalman filter; PF-particle filter; CNN-convolution neural network; RGB-D-red-green-blue-depth; RMS-root mean squares; TDoA-time-difference-of-arrival; RFID-radio frequency identification; LED-light-emitting diode; RSS-received signal strength; AP-access point; WiFi-wireless fidelity; BLE-Bluetooth low energy; N/A-not provided.…”

Outdoor Target Positioning Using Wii Remote IR Camera and Signal Modulation

“…Unfortunately, the aforementioned studies are all developed for indoor use and hence, it is not applicable to outdoor applications. A similar idea for outdoor target localization is introduced in [18], where ultraviolet LED markers are used instead of IR LEDs. In this research, it is claimed that the ultraviolet light in the normal sunlight is significantly less intense and thus, the natural environments are normally too dim to prevent the detection from the camera.…”