| dc.description.abstract | RFID systems are a commonly used method of identifying objects, and the use of RFID for high precision localization is of growing interest. RFID is a promising method for the unique identification of autonomous vehicles within a larger system, such as infrastructure enabled autonomy. This paper describes a scheme for tracking the location of autonomous vehicles using on-board battery-assisted passive RFID tags. The localization method described relies on the physical principle that the phase of a radio signal varies linearly with the distance between the transmitting and receiving antenna. The measured phase difference is used in conjunction with frequency hopping to overcome the natural ambiguity of the phase measurements to calculate the distance between a single RFID antenna and tag. A Kalman filter was also developed and implemented to demonstrate the performance of the localization method when filtered. The proposed algorithm was implemented and tested using ROS. The Impinj Speedway R220 RFID reader was used for testing, and communication with the RFID reader was implemented using the Impinj Octane SDK. Testing included both static and mobile experiments. Static tests showed consistent localization out to 40 meters. The Kalman filter successfully removed bad estimates and converged quickly to the true distance. The static tests also confirmed that the algorithm is successful even when the antenna is off-angle from the RFID tag. The mobile experiments did not demonstrate successful localization, likely due to an error when testing which caused only a coarse velocity measurement to be obtained. This experiment will be repeated with a more accurate velocity measurement to determine the effect that movement has upon the described algorithm. The main contribution of this research is the completely novel, phase-based localization method for RFID. Preliminary experimentation was performed as a proof-of-concept for this approach, but there are still many open-ended questions. Localization was performed between a single tag and a single antenna, but the method could be extended to multi-tag or multi-antenna localization. Additionally, the method still needs to be demonstrated for localization of a mobile tag. | |
