The 7th IFAC Symposium on Intelligent Autonomous Vehicles 2010

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Real-time Ray-tracing for Underwater Distance Evaluation with Application to Distributed Localization of AUV Teams

Giuseppe Casalino
DIST- University of Genova, Genova, Italy
Italy

Andrea Caiti
DSEA-University of Pisa, Pisa, Italy
Italy

Alessio Turetta
DIST- University of Genova, Genova, Italy
Italy

Enrico Simetti
DIST- University of Genova, Genova, Italy
Italy

Abstract:
The paper deals with the problem of distributed acoustic localization of teams of Autonomous Underwater Vehicles (AUVs) and proposes a novel algorithm, Real-Time Ray-Tracing (RT2), for evaluating the distance between any pair of AUVs in the team. The technique, based on a modified formulation of the non%linear sound-ray propagation laws, allows efficiently handling the distorted and reflected acoustic ray paths, induced by the anisotropy of the underwater medium. Further it can be easily implemented on-board of low-cost AUVs. Indeed it just requires the presence, on each vehicle, of a simple acoustic modem and a pair of look-up tables, a-priori constructed via the assumed knowledge of the depth-dependent sound velocity profile. On such a basis, every AUV can easily on-line compute its distance w.r.t. to any other neighbour team member, through time-of-flight measurements and the exchanges of depth information only. Further, since the proposed RT2 algorithm makes available accurate distance evaluations (despite the distorted acoustic rays), the effective filtering techniques normally
used by terrestrial mobile robots for distributed localization are expected to be transferable to the underwater field.

 

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