Real-time, robot-based, 3D localization of RFID tags, by transforming phase measurements to a linear optimization problemReal-time, robot-based, 3D localization of RFID tags, by transforming phase measurements to a linear optimization problem Peer-Reviewed Journal Publication Δημοσίευση σε Περιοδικό με Κριτές 2023-11-142022enThis work was supported by the European Union and Greek National Funds through the Operational Program Competitiveness, Entrepreneurship and Innovation, under the call RESEARCH—CREATE—INNOVATE under Project T2EDK-02000.In this paper, we propose a prototype method for fast and accurate 3D localization of RFID-tagged items by a mobile robot. The robot performs Simultaneous Localization of its own pose and Mapping of the surrounding environment (SLAM). It is equipped with RFID readers and antennas placed at different heights, collecting phase-measurements by all tags. Thanks to the self-localization property of the robot, a synthetic aperture is created for each tag. In this paper, we have manipulated the set of phase-measurements, combined with the known poses of the robot to craft an overdetermined system of linear equations which pinpoints the location of the tag. The linearity of the system preserves that localization is achieved rapidly. The problem is solved for any arbitrary movement of the robot and extended in three dimensions. The proposed method is experimentally compared against the state-of-the-art in SAR-based RFID localization. It is the fastest and the most accurate, when the robot moves along straight-paths. Its accuracy slightly worsens, when the robot moves along non-straight paths, while preserving its exceptionally small running-time. It can be applied in real-time 3D localization problems, demonstrating mean 3D accuracy below 20 cm.http://creativecommons.org/licenses/by/4.0/IEEE Journal of Radio Frequency Identification6439-455 Tzitzis Anastasios Malama Andreana Drakaki Vasiliki Bletsas Aggelos Μπλετσας Αγγελος Yioultsis Traianos Dimitriou Antonis G. Institute of Electrical and Electronics Engineers RFID Localization Linear optimization SAR Phase unwrapping Confidence evaluation Robotics SLAM