engleski

Control of autonomous surface marine vessels for underwater vehicle localization using single range acoustic measurements

The interest in marine environment (underwater and surface) constantly increases, both for scientific and economic reasons. In order to accomplish many tasks in such environment, reliable localization of underwater objects is necessary. The cost of the conventional underwater localization systems can compromise a significant share of the total vehicle cost. The focus of this thesis are control algorithms for autonomous surface marine vehicles that are equipped with affordable acoustic sensors and whose goal is localizing or enhancing underwater localization of the objects of interest. Mobile beacon vehicles are used as a navigational aid for autonomous underwater vehicles when performing navigation using single range measurements. They remove the constraints imposed on the underwater vehicle trajectory by executing trajectory that provides informative range measurements. In thesis, control algorithm for the beacon vehicle which ensures observability of the underwater vehicle’s navigation filter is presented. It is characterized by a small communication overhead, low computational complexity and it is deployable on both fully actuated and underactuated vehicles. The algorithm was tested in real–life environment and the acquired experimental results were validated using a metric proposed in the thesis. Control algorithm for an autonomous surface system carrying a two-sensor array consisting of two acoustic receivers, capable of measuring the time difference of arrival of a quasiperiodic underwater acoustic signal and utilizing this value in order to steer the system towards the acoustic source in the horizontal plane, is another major contribution of the thesis. Stability properties of the proposed algorithm are analysed using the Lie bracket approximation technique. Furthermore, simulation results are shown, where particular attention is given to the influence of a constant disturbance caused by sea currents and a relationship between the time difference of arrival measurement noise and the sensor baseline. Experimental results in which the algorithm was deployed on two autonomous surface vehicles, each equipped with a single acoustic receiver, are presented. The algorithm successfully steers the vehicle formation towards the acoustic source, despite the noisy and intermittent measurements, thus showing the feasibility of the proposed algorithm in real-life conditions.

underwater localization ; single range measurements ; navigation ; mobile beacon ; source seeking ; time difference of arrival ; autonomous surface vehicles

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