Phase ReLock - Localization of RFID Tags by a Moving Robot

In this work, we propose a prototype method for the localization of RFID tags, by deploying RFID equipment on a robotic platform. The constructed robot is capable to perform Simultaneous Localization (of its own position) and Mapping of the environment and then locate the RFID tags around its path. The proposed method is based on properly treating the measured phase of the backscattered signal by each tag at the reader's antenna, located on top of the robot. More specifically, the measured phase samples are reconstructed, such that the 2π discontinuities are eliminated. This allows for the formation of an optimization problem, which can be solved rapidly by standard methods. The proposed method is experimentally compared against the most accurate reported method in prior-art and the same accuracy is preserved. However, the problem is solved more than one order of magnitude faster, allowing for the applicability of the method in real-time inventorying and localization.