Automated robot docking using direction sensing RFID

Automated target acquisition and docking is key to enabling various applications of autonomous mobile robots in indoor environments. For the purpose, many researches have been devoted to the development of location sensing techniques employing the latest in RFID or GPS. However, it has not yet become possible to attain high accuracy in those techniques, particularly in cluttered or dynamically changing environments. In this paper, we propose a novel location sensing RFID reader equipped with a dual directional antenna that communicates with controllable RF transponders. The dual directional antenna estimates the direction of arrival (DOA) of signals from various transponders by using the ratio of the received strength between two antennas. This enables the robot to continuously monitor the changes in the ratio and find its way to the target transponder. To verify the validity of the proposed system in real environments populated with unknown obstacles, we perform detailed experiments using simulations and hardware implementations. Specifically, the target acquisition and docking guidance are demonstrated in a multiple transponder environment under various circumstances.