Enhanced, embodied autonomy in small submersibles enables the design and deployment of practical swarms of autonomous underwater vehicles (AUVs). The swarming paradigm requires for each vehicle location awareness of at least its near neighbors. The Serafina AUV swarming project additionally requires a localisation system which could cope with the dynamic and fast changing vehicle configurations while being small, reliable, robust, and energy efficient and not dependent on pre-deployed acoustic beacons.
The short-range acoustical relative localisation system proposed here, uses hyperbolic and spherical localization concepts and provides each vehicles with the azimuth, range and heading of its near neighbours. The implementation utilises an acoustically transmitted MLS)signal which provides extremely high robustness against interference by stochastic and systematic disturbances which are typical for underwater environments. The azimuth is obtained via hyperbolic positioning with improved resolution and accuracy with respect to conventional methods. Range and heading estimation is achieved by two independent methods for increased robustness; one uses the implicit synchronisation provided by the underlying inter-vehicle communication scheduling system to measure the difference of TOAs of an acoustic and a long-wave radio signals; the second relies on TDOAs and a reverse hyperbolic localisation scheme.

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