This paper reports recent experimental results in the development and deployment of a synchronous-clock acoustic navigation system suitable for the simultaneous navigation of multiple underwater vehicles. The goal of this work is to enable the task of navigating multiple autonomous underwater vehicles (AUVs) over length scales of O(100 km), while maintaining error tolerances commensurate with conventional long-baseline transponder-based navigation systems (i.e., O(1 m)), but without the requisite need for deploying, calibrating, and recovering seafloor anchored acoustic transponders. Our navigation system is comprised of an acoustic modem-based communication/navigation system that allows for onboard navigational data to be broadcast as a data packet by a source node, and for all passively receiving nodes to be able to decode the data packet to obtain a one-way travel time pseudo-range measurement and ephemeris data. We present results for two different field experiments using a two-node configuration consisting of a global positioning system (GPS) equipped surface ship acting as a global navigation aid to a Doppler-aided AUV. In each experiment, vehicle position was independently corroborated by other standard navigation means. Initial results for a maximum-likelihood sensor fusion framework are reported.

This paper describes the in-field operation of two interacting autonomous marine vehicles to demonstrate the suitability of interval programming (IvP), a novel mathematical model for multiple-objective optimization. Broadly speaking, IvP coordinates competing control needs such as primary task execution that depends on a sufficient position estimate, and vehicle maneuvers that will improve that position estimate. In this work, vehicles cooperate to improve their position estimates using a sequence of vehicle-to-vehicle range estimates from acoustic modems. Coordinating primary task execution and sensor quality maintenance is a ubiquitous problem, especially in underwater marine vehicles. This work represents the first use of multiobjective optimization in a behavior-based architecture to address this problem

The major focus of the Acoustic Telemetry Group at Woods Hole Oceanographic Institution has been the development of underwater acoustic communication and remote sensing devices. These are typically deployed in buoys, underwater vehicles, or in ocean-bottom packages. The devices communicate acoustically with a surface station, conveying scientific results to observers, and accepting commands. A significant milestone in the evolution of such platforms has been the development of an operating system (called AMS) for embedded signal processing. This system allows rapid algorithm prototyping using a high-level, matrix-based language specialized to DSP targets and real-time data-flow processing. A key feature of AMS, distinguishing it from other high-level DSP specification software, is that the language is interpreted as well as executed by the target DSP. Performance is maintained by (i) coding time-critical algorithm steps in C or assembly language, and (ii) using multiple DSP devices in a loosely-coupled network. The motivation for, and development of, the AMS Operating System are reviewed. The potential for rapid algorithm prototyping using AMS is demonstrated by way of two applications in underwater acoustic signal processing.