Design and development of a localization system for a sensor network in collective symbiotic organisms

Abstract

The REPLICATOR project aims for developing self-adaptive and self-assembling organisms compounded of stand-alone robots. These robots can autonomously and dynamically dock with each other forming symbiotic structures. This system requires that each robot knows the position of the others. Therefore, this master thesis consists of the design, implementation and assessment of a low power and low cost localization system, based on the strength of the signal of the wireless communications protocol ZigBee. Furthermore, a dynamic ZigBee coordinator selection process was developed to separate the localization application and the system’s configuration. The proposed solution is a distributed, anchor-free, self-configuring, cooperative and concurrent algorithm. The localization is iteratively recalculated and updated using a Eucledian method. In order to reduce the errors produced by the fluctuations of the signal, a weighted approach, IIR and FIR filters; and a calibration process were implemented. It was found that the implemented localization system can achieve localization errors lower than five percent. However, these errors vary greatly depending upon several uncontrolled facts such as the environment in which the system is deployed and the radiation pattern of the antennas; and in addition, the errors increase exponentially with the distance.