A ZigBee-based framework for approximating sensor range and bearing

An open hardware framework for approximating range and bearing of radio frequency (RF) sensors is presented. The current work has an immediate application in solving the simultaneous localization and mapping problem which is one of the challenging problems in the field of robotics. In this work, a set of RF sensors utilizing the ZigBee protocol are placed in an indoor environment and a base RF sensor is mounted within a rotating parabolic reflector on a mobile robot. The proposed range and bearing approximation framework works in two cascaded phases. In the first phase, the base RF sensor sends an RF signal to all other RF sensors within its operating range. These RF sensors then respond to the base RF module where ZigBee packets are parsed to store raw data for approximating range. In the second phase, a stepper motor is employed to rotate the parabolic reflector and the base RF sensor mounted on the robot. These two phases continue until a full revolution of 360° has been achieved. The data is processed for approximating the bearing of each RF sensor with respect to the mobile robot's heading angle, as well as the distance (range) to the RF sensor at its associated bearing. The proposed hardware setup is validated through a set of experimental results gathered in an indoor environment.