A UHF RFID-Based Dynamic Object Following Method for a Mobile Robot Using Phase Difference Information

Dynamic object following is an essential ability for mobile robots in various application scenarios such as auxiliary cargo transportation, disabled assistant caring, and multirobot formation. A dynamic object following method for a mobile robot based on ultrahigh-frequency (UHF) radio frequency identification (RFID), which uses a phase difference information-based dynamic following model, is presented in this article. Through this method, a mobile robot equipped with an RFID reader can follow a dynamic target object attached with a passive RFID tag. A cost function is constructed to indicate the changes in relative distance and bearing between the target object and the following robot, allowing the real-time calculation of the translational and rotational velocities of the following robot using an algorithm base on proportional integral differential (PID)-based controllers. Compared with the existing RFID-based following methods, the proposed method can achieve a satisfactory distance and bearing following accuracy by using RFID phase difference information without any tedious and time-consuming phase drift or antenna installation calibration. Real experiments were conducted using commercial off-the-shelf (COTS) UHF RFID, and results show that the proposed method is effective and robust, the respective average distance and bearing following errors were approximately 1.65 cm and 4.94° during the robot-following tests and 4.45 cm and 6.03° during the human-following tests. The proposed method has promising applications in mobile robot following of dynamic object to provide service or assistance in large storage and manufacturing industries.