LAIDR4D: Compass-Free Global 4D Pose Tracking of Lighter-Than-Air Indoor Robot Using UWB Ranges

The autonomous navigation of lighter-than-air indoor robot (LAIDR) demands accurate 4D pose (3D position+1D heading) tracking. Usually, the vision and compass-based sensing systems estimate the 4D pose. However, these sensing systems suffer from indoor light and magnetic field conditions and require the building frame's alignment. This paper proposes an ultra-wideband (UWB) ranging-based compass-free 4D pose tracking of LAIDR named LAIDR4D. The hardware and software of UWB sensors are devised in-house to achieve a compact size, lightweight, and flexible system customization. The low-level firmware is designed using a double-side two-way ranging technique to measure the twin-tag UWB ranges without requiring the clock-synchronization. The high-level localization is developed using a twin-extended Kalman filter to deal with the non-linearity of the UWB ranges. Finally, the extensive evaluation shows that the LAIDR4D can reflect root-mean-square-error (RMSE) of under 0.20 m and 3.0° for the 3D positioning and heading, respectively.