Open Loop Swimming Performance of ‘Finnegan’ the Biomimetic Flapping Foil AUV

Finnegan, the Massachusetts Institute of Technology Biomimetic Flapping Foil Autonomous Underwater Vehicle (BFFAUV), was developed to explore the use of two degree of freedom oscillating foils as the sole means of propulsion and maneuvering for an underwater vehicle. Two pairs of foils with 0.4m span x 0.1m chord are used, with one pair forward and one pair aft of the center of gravity, with the mean position of each foil in the horizontal plane. Experimental results are presented for open-loop speed trials in each of four degrees of freedom: surge, sway, yaw and heave. Foil kinematics which generate thrust through lift-based fluid dynamics are used to actuate vehicle surge and yaw, while a drag-based or ‘rowing’ style is used to actuate sway and heave. The vehicle demonstrates high performance in the lift-based modes of locomotion, achieving a maximum surge speed of 1.38 meters per second and yaw rates of 80.2◦ per second. Using the drag-based rowing motion, heave and sway velocities of 0.40 meters per second and 0.46 meters per second, respectively, were achieved. In addition to allowing characterization of vehicle performance, preliminary operational testing yielded insights into the challenges of joystick based manual control of a flapping foil vehicle. Two different mappings between joystick input and foil action are presented.