GuideAndTrack: A Novel Guidance and Localization Method by a Handheld UHF-RFID Reader

Abstract

In this paper we present GuideAndTrack; a prototype method for guiding a user to any RFID-tagged target. The user is equipped with a handheld RFID reader, which measures the phase of RFID tags placed at known positions in the map. Motion of the user is captured by estimating the Rate Of Change (ROC) of the collected phase measurements along discrete time-slots; i.e. null rate implies zero radial vector with respect to the corresponding tag, while negative/positive rates signify approaching towards or moving away from the corresponding tag respectively. The phase ROC represents an advantageous metric for accurate localization, since it can be easily measured in any given time-slot and does not necessitates knowledge of the prior state of the reader-to-tag link. The proposed method, initially estimates the direction of motion of the user, by sorting the estimated phase-ROCs from the surrounding tags during one’s translational motion, guiding one to the desired target. Then, the position of the user is accurately estimated by feeding the estimated phase-ROCs in a particle filter. The proposed method has been experimentally verified in two cases; one by deploying a robot, in order to acquire the ground truth of the moving “user” and another case, where a human held a portable RFID reader. In all cases, the method performed well, guiding the user to the desired target, while estimating one’s pose accurately. Characteristic results and comparison with prior art are presented herein.