AUV behaviors for collection of bistatic and multistatic acoustic scattering data from seabed targets

Abstract

Characterization of seabed targets using networks of Autonomous Underwater Vehicles (AUVs) is of great interest for harbor security. The imaging sensors generally used for target localization and classification are expensive for outfitting multiple AUVs and produce data that is difficult to use for realtime onboard classification. An approach to this problem has been developed in which an acoustic source insonifies targets and AUVs with inexpensive hydrophone nose arrays are used to sample the resulting scattered fields. These scattered fields consist of distinctive radiation patterns, where the amplitude sampled by a receiving AUV for a particular target is determined by source frequency, aspect angle between source and target, and bistatic angle between source and receiver. AUV behaviors were developed to control the bistatic angles relative to a localized target between source and receiver vehicles and aspect angle between a target and the source. Two configurations were explored: bistatic, where the source is fixed and receiver moving, and multistatic, where both source and receiver are located on mobile autonomous vehicles. Design considerations for behaviors to sample different combinations of bistatic angle and aspect angle included keeping receiving arrays broadside to a target for uniform-quality data collection and obeying vehicle dynamics constraints. Behaviors for the bistatic configuration were demonstrated in AUV experiments, and behaviors for the multistatic case were demonstrated in simulation, including collaboration between source and receiver vehicles for controlling bistatic versus aspect angle.

Multistatic acoustic characterization of seabed targets

“…A description of several possible multistatic sampling behaviors can be found in Ref. 28. In one promising multistatic sampling behavior, the constant-bistatic-angle or CBA behavior, the source vehicle and one or more receiver vehicles circle the estimated target location at constant radii while maintaining selected bistatic angles between source and receivers.…”