RFID-Assisted Robot Navigation

Among others, in the last years, RFID technology has been approached also by robotics researchers focused on navigation tasks dealing with indoor mapping and localization. In fact, in such a context, if passive tags are used as landmarks and the robot is equipped with a reader, RFID technology does naturally become a significant and cost-effective support for mobile robot navigation and localization.
In such a context, it is worth pointing out that unsatisfactory performance stated in literature so far, are substantially due to the fact that commercial and general-purpose RFID systems — whose properties should be adequate in a wide range of applicative contexts — are used. It is worth observing, though, that long range working distances guaranteed by canonical tags, may increase multipath and false positive/negative readings. Moreover, label-type tags are strongly platform dependent, so that their performance are influenced by the platform on which they are attached to.
Finally, from the RFID reader point of view, since in many applications the orientation of a linearly polarized tag is unknown a priori, commercial reader antennas must be circularly polarized. Moreover, as requirements in terms of size and weight are not essential, most of commercial RFID reader antennas are usually not miniaturized. In robotic context, some of the features of commercial RFID systems might become inessential or even unfavorable. Vice versa, some others would be strongly desired.
For these reasons, in the RFID division of EML2, the opportunity to improve the performance of a RFID-assisted system for indoor mobile robot navigation is investigated by defining, designing and testing new RFID devices. The specific requirements are identified and both reader and tag antennas tailored for the specific application are designed (see Fig. 1 and Fig. 2).

Fig. 1. Studied reader antenna (left) with simulated pattern radiation (right).

Fig. 2. Prototype of the tag proposed for robotic applications. It is a platform tolerant, medium-range, fully-passive RFID tag whose performance is not affected by the application surface .

In particular, a compact and lightweight linearly polarized reader antenna has been realized. It is based on a planar Yagi-Uda structure with meandered driven dipole and concave parabolic reflector. Moreover, a new simple and low-cost platform-robust tag exhibiting similar performance on any platform (including metal) has been designed and realized.
The new hardware has been then tested in different practical robotic applications with the aim of estimating tag and robot reciprocal positions. Test results are impressive and conceptually demonstrate that a RFID solution properly customized for the addressed application, strongly improves the overall performance.