High Availability Acoustic Positioning for Targets Moving in Poor Coverage Areas

Abstract

Currently, most acoustic positioning strategies are based on broadband coding and the pulse compression technique to obtain better accuracy and robustness against in-band noise. However, the accuracy and robustness of these systems are often seriously damaged in areas of low coverage and/or affected by multipath. This work proposes a high availability positioning algorithm (HAPA) that optimally processes the received signal to improve positioning results throughout the whole location area. This algorithm validates the Time-of-Arrival (ToA) from each beacon, corrects their Doppler shift, and compensates for multipath when it exists. If the number of validated beacons is enough to obtain a position, the algorithm tries to position with their optimal combination; if not, it tries to position by incorporating additional ToA candidates for the nonvalidated beacons. The HAPA performance has been evaluated through a set of experimental tests to compare its results with those obtained by the robust positioning algorithm (RPA) developed by the authors in previous work, and by a classical positioning algorithm (CPA) based on the emission of chirps. In particular, when using a mobile robot to follow trajectories that cross areas with low coverage and affected by multipath, the HAPA maintains availability of 97.89%, while the RPA drops to 83.25% and the CPA to 50.19%.