Towards Selective Tidal-Stream Transport for Lagrangian profilers

Autonomous Lagrangian profilers are widely used as measurement and monitoring platforms. In their current mode of operation, the profilers usually drift passively at their parking depth before making a vertical profile to go back to the surface. This paper presents a control strategy to actively select and use tidal currents so that a profiler can autonomously reach a desired destination. After presenting the profiler and possible modifications for a coastal environment, we introduce simple mathematical models for the profiler and its environment. We then present a feedback controller that, taking into account the direction of oscillating tidal currents, is able to steer the profiler to any horizontal location. For illustration, we also give a few simulation results using tidal current data from the North Sea.