Autonomous underwater vehicle self-localization using a tetrahedral array and passive acoustics

Abstract

The recent development of very low-cost, miniature autonomous underwater vehicles (AUVs) has lowered the barrier toward the deployment of multiple AUVs for spatially distributed sensing. However, these AUVs introduce size, power, and cost constraints that prevent the use of traditional approaches for vehicle self-localization, such as Doppler velocity log (DVL)-aided inertial navigation. In this work, we describe a system that estimates the vehicle's position relative to a single acoustic transmitter. The transmitter periodically outputs a linear up-chirp that is synchronously recorded by a tetrahedral ultra-short baseline (USBL) hydrophone array on the AUV. Real-time 3D phased-array beamforming and matched filtering is performed on-board the vehicle, and integrated with AUV pitch-roll-heading to calculate azimuth, inclination, and range measurements to the transmitter. Finally, a particle filter incorporates these measurements with vehicle speed estimates and a motion model to generate a positional likelihood for the acoustic transmitter relative to the AUV. This system enables vehicle self-localization in the case where the transmitter is stationary, and is entirely passive on the vehicle, allowing multiple AUVs to localize using a single transmitter. We describe the processing pipeline of our system, and present results from AUV field experiments. [Work supported by Battelle, ONR, Lincoln Laboratory and DARPA.]