Control of a Bio-inspired Vessel with Undulating Fin Propulsion Swimming Behind a Flat Plate.

Navigating through unsteady flow environments dominated by vortex shedding presents significant challenges for both biological swimmers and underwater robotic systems. These fluid regions exhibit dynamic and spatially varying forces that can disrupt locomotion, destabilize orientation, and increase the energy demands of robotic vessels. However, these hydrodynamic could presents some beneficial interaction to improve efficiency or enhance maneuverability. To perform effectively in such complex fluid conditions, underwater vehicles must utilize advanced control strategies that ensure accurate positioning while minimizing energy consumption by taking advantage of vortex shedding. In this work, we explored swimming dynamics and control of a bio-inspired vessel that uses a single flexible fin that runs along the bottom of the robot to perform forward and directional swimming. The objective of this study was to evaluate the position and directional control strategies like robot’s ability to maintain station-keeping, optimize energy efficiency, and ensure maneuverability when swimming in an unsteady wake generated from fixed flat plate. The experiments were conducted in a water flume where a fixed flat plate obstacle was placed in the test section to generate unsteady wake flows through vortex shedding. The robot was positioned downstream of plate within the field of view of a camera mounted above the flume for real-time tracking. Multiple tests were conducted at varying flow speeds and different control positions. Additionally, the strength and size of the vortices were modulated by altering the width of the flat plate relative to the fin dimensions of the robotic vessel. Our results showed that simultaneously modifying the fin's curvature by adjusting the colliding point of opposing sinusoidal waves produced a net yaw torque, enabling heading control and bidirectional thrust. In this work we will present different control strategies and evaluate their performance for precise position control and efficiency.