Design and projected performance of a flapping foil auv

Abstract—The design and construction of a biomimetic flapping foil autonomous underwater vehicle is detailed. The vehicle was designed as a proof of concept for the use of oscillating foils as the sole source of motive power for a cruising and hovering un-derwater vehicle. Primary vehicle design requirements included scalability and flexibility in terms of the number and placement of foils, so as to maximize experimental functionality. This goal was met by designing an independent self-contained module to house each foil, requiring only direct current power and a connection to the vehicle’s Ethernet local area network for operation. The re-sults of tests on the foil modules in the Massachusetts Institute of Technology (MIT) Marine Hydrodynamics Water Tunnel and the MIT Ship Model Testing Tank are both used to demonstrate funda-mental properties of flapping foils and to predict the performance of the specific vehicle design based on the limits of the actuators. The maximum speed of the vehicle is estimated based on the limi-tations of the specific actuator and is shown to be a strong function of the vehicle drag coefficient. When using four foils, the maximum speed increases from 1 m/s with a vehicle of 1.4 to 2 m/s when = 0 1, where is based on vehicle frontal area. Finally, issues of vehicle control are considered, including the decoupling of speed and pitch control using pitch-biased maneuvering and the tradeoff between actuator bandwidth and authority during both the cruising and hovering operation. Index Terms—Biomimetic propulsion, flapping foils, underwater vehicles. I