Study case scenario

 


                           UNDERWATER SOURCE DETECTION AND TRACKING

     


   
  The study scenario is a “gradient search and following for [x] source detection” mission (where [x] is representing the nature of the source to be detected : fresh water, chemical source, methane vent,….); The objective of the mission is to detect and follow gradients of concentration of the source flow by considering sensed data provided by dedicated scientific sensors located on-board the AUVs. The vehicle baseline configuration (the formation pattern) must be such that spatial estimates of the gradient of the source concentration can be computed co-operatively. It is up to the fleet to manoeuvre so as to seek the region of higher concentration, and thus the localisation of the source (see above).

    The search phase will be classically performed by planning a meander-like track pattern. The main advantage of using multiple systems in a co-ordinated motion is the extension of the sensor range with respect to area coverage or depth coverage. This is especially important if properties which shall be measured fluctuate with time.

    When the expected data are measured by the detection sensors, the trajectory to be followed by the fleet shifts from the predefined search pattern to a sensor-based trajectory control in order to detect the source of the measured data.

     For this proposed scenario, it is of interest that information is exchanged between sensors operated by individual vehicles in order to build up the gradient shape and location from which a trajectory for the fleet of vehicles will be calculated.

     To perform mission involving several vehicles, coordinated motion is required, especially when the goal of the mission is sensor driven. In the case presented here, the detection of the source can only be performed with the sensor information collected by the vehicles measuring concentration in the source plume. 

    During all the mission duration, the ASVs fleet at the surface should remain in adequate configuration with respect to the AUVs fleet. This configuration (mainly relative positioning) must guaranty reliability of the communication with the AUVs group and with the support ship (see Figure).