DEVELOPMENT OF AN UNDERWATER FLAPPING FOIL TOW-TEST SYSTEM

Abstract

Autonomous Underwater Vehicles (AUVs) using conventional methods of propulsion cannot operate in a dynamic environment such as the surf zone or around a reef. Bio-inspired propulsion mechanisms can provide the capabilities required to deal with the hazards of these locations. Animals such as birds, fish, and turtles use flapping foils as a means of propulsion and high maneuverability. Robotic flapping foils can be applied similarly to underwater vehicles like the AUV, Finnegan the RoboTurtle from MIT. Finnegan used four flapping foil turtle each with two degrees of freedom. One of those fins was outfitted to house force sensors which could provide instantaneous measurements of the forces acting on the foil. The purpose of this project, is to create a system capable of testing submerged underwater flapping foils in a tow-tank using force sensors to detect fluid flow phenomena. The force sensors had to be tested, installed, and calibrated so that they measured the forces about the desired axes. A method of attaching the fins to the towing carriage had to be devised and built out of aluminum. This attachment had to be sturdy due to dynamic loading and life expectancy for future use, streamlined where it would be submerged, and user friendly. The attachment also had to be able to adjust the depth of the fin. A data acquisition system was setup to record and transfer the force sensor measurements and foil positioning data from the towed flapping foil to the computer station. Tests were run to compare to past data in an effort to validate the testing system. The system can collect valid data currently, but improvements are necessary to achieve the desired functionality.