Augmented Reality and UWB Technology Fusion: Localization of Objects with Head Mounted Displays

Abstract

Technical advances in computer vision, visual inertial odometry and display technology in the past years have produced a considerable improvement in Augmented Reality (AR). However, none of the contemporary commercial Head-Mounted Displays (HMDs) locates objects that are not in direct line-of-sight with a camera. Our objective is the localization of unseen objects and their visualization through an AR HMD. We extend the functionality of an AR HMD by integrating an ultra-wideband (UWB) transceiver on a Microsoft HoloLens. The UWB transceiver estimates the distance to another UWB transceiver via time of arrival. For UWB ranging, two different protocols have been proposed by the IEEE 802.15.4a-2007 standard: Two-Way Ranging (TWR) and Symmetric Double-Sided Two-Way Ranging (SDS-TWR). In this work we consider three different TWR implementations and the standard SDS-TWR method. Two of the three implemented TWR methods use a DecaWave DW1000 IC utility for estimating the clock frequency offset. Our method processes this data with a digital low-pass filter in order to remove the fluctuations induced by the frequency offset estimation error. We localize a static UWB transponder with trilateration, given the measured distance and the calculated positions of the integrated UWB antenna in the HoloLens coordinate frame. We measure and compare the accuracy and precision achieved with three different implemented TWR ranging methods and SDS-TWR. The precision achieved with our TWR method even surpasses SDS-TWR in our measurements. We localize and visualize the estimated position of the UWB transceiver in the HMD with an accuracy of 6 cm for position dilution of precision (PDOP) values smaller than 10.