A restarting paradigm for a Range-Only SLAM algorithm using the phase of passive UHF-RFID signals

Sensors based on the phase-shift of UHF-RID signals provide sharp but ambiguous tag-reader distance measurements. Despite the ambiguity, Range-Only SLAM algorithms, suitably modified, have been adopted in previous works to obtain satisfactory solutions to the SLAM (Simultaneous Localization and Mapping) problem. The performance is often comparable to the one achieved using unambiguous range sensors with similar precision (e.g. laser). However, the cycle ambiguity of phase measurements can deteriorate the performance of the algorithm and, in some cases, can even lead to divergence. In this paper we present some ideas to overcome this problem by introducing a restarting paradigm. This requires the definition of a diagnostic module, in charge of understanding if the filter is diverging, and of a restarting procedure, for a (partial) reinitialization of the estimation process.