Discussion on the forward-backward configuration effect of reader antennas in a floor-installed RFID system

A significant discussion is provided on the configuration of reader antennas (RAs) affecting a robot's positioning performance in a floor-installed RFID infrastructure for two-wheeled robots. RFID systems where IC tags are installed under/on floors have been widely utilized for positioning infrastructures. The RAs should be properly placed on a robot so that such an environment can give full play to its potential capabilities of positioning the robot. This problem calls for guidelines in designing the configuration of RAs. Our previous simulation study extracted an effect involving RA configuration in front of and behind the robot's moving direction (the forward-backward configuration effect), which can be a critical parameter for positioning accuracy, while it lacked a full investigation of the cause of the effect. This paper not only discusses an extraction of the effect, but also presents a detailed discussion on how it occurs through data analysis, a mathematically schematic proof and a control experiment for validation. Our discussions are widely applicable to localization methods using landmarks on/under the floor because our model assumes a simple and general detecting condition.