Abstract-Photographic surveys of the seafloor with flight style autonomous underwater vehicles are a very effective tool for discovery and exploration. Due to the high terrain collision risk for the survey vehicle, they are employed with caution. The extent of this risk remains unquantified. For mission planning, researchers and vehicle operators have to rely on their experience. This paper introduces measures for vehicle risk and success and analyses how previously mapped terrains and artificially generated terrain maps can be used to categorize terrains. The developed measures are applied to a simulation of the Autosub6000 flight style AUV terrain following system. Based on quantitative parameters, changes to the obstacle avoidance system and survey mission plans can be better informed.
Operating an autonomous underwater vehicle (AUV) in close proximity to terrain typically relies solely on the vehicle sensors for terrain detection, and challenges the manoeuvrability of energy efficient flight‐style AUVs. This paper gives new results on altitude tracking limits of such vehicles by using the fully understood environment of a lake to perform repeated experiments while varying the altitude demand, obstacle detection and actuator use of a hover‐capable flight‐style AUV. The results are analysed for mission success, vehicle risk and repeatability, demonstrating the terrain following capabilities of the overactuated AUV over a range of altitude tracking strategies and how these measures better inform vehicle operators. A major conclusion is that the effects of range limits, bias and false detections of the sensors used for altitude tracking must be fully accounted for to enable mission success. Furthermore it was found that switching between hover‐ and flight‐style actuations based on speed, whilst varying the operation speed, has advantages for performance improvement over combining hover‐ and flight‐style actuators at high speeds.
Abstract-A current challenge for AUV missions is to combine long endurance with high manoeuvrability. The proposed Pipefish AUV is a long endurance AUV capable of high quality survey missions that can deliver multiple hover capable AUVs to sites of interest. The Pipefish AUV and the small vehicles can perform cooperative tasks and reach remote locations without the need for a monitoring surface vessel. It is shown that an endurance of six days can be achieved, whilst transporting smaller AUVs of a volume of almost two cubic metres.
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