An RFID-based ranging system for worker safety in agricultural working areas

This paper proposes a passive RFID-based Ranging System to enhance the worker safety in agricultural and forestry working areas where remote-control farm machineries and human workers co-exist. It is conceived within the SMARTGRID Project co-funded by the National Institute for Insurance against Accidents at Work, INAIL. Workers and obstacles are equipped with multiple passive UHF-RFID tags, whereas the reader-equipped machinery is able to determine its distance from tags according to an amplitude-based ranging method which exploits a two-rays electromagnetic channel model. Such signal model is here firstly presented and discussed. In particular, it is based on the received power ratio from a couple of tags to release from the knowledge of the tag backscattered gain thus avoiding calibration procedures typical of classical amplitude-based methods. After a numerical analysis to investigate the effect of several system parameters, the signal model is validated through a preliminary experimental campaign in the context of the SMARTGRID Project. Such a ranging system can increase the safety of workers when accompanied by an alarm system which signals any potential collision occurring in the working areas.