DESIGN AND PERFORMANCE OF A FISH FIN-LIKE PROPULSOR FOR AUVS

Fishes are noted for their ability to maneuver and to position themselves accurately even in turbulent flows. This ability is the result of the coordinated movement of fins which extend from the body and form multidirectional control surfaces that allow thrust vectoring. We have embarked on a research program designed to develop a maneuvering propulsor for AUVs based on the mechanical design and performance of fish fins. To accomplish this goal, we have taken a fivepronged approach to the analysis and design of a propulsor based on principles derived from the study of fish fin function. First, we have undertaken a detailed investigation of 3D kinematic patterns exhibited by fish fins during locomotion. Second, we have measured the mechanical properties of fish fin rays and membrane that comprise the propulsive surface. Third, we have studied the hydrodynamics of fish fin function using digital particle image velocimetry (DPIV) on the fins of freely swimming fishes. Fourth, a computational fluid dynamic (CFD) study of fish fin function has been produced that allows calculation of fin flow patterns using actual 3D fish fin kinematics and allowing bending and fin area changes during the fin stroke. Fifth, a first generation biomimetic, physical, robotic model of the bluegill sunfish pectoral fin has been developed that can reproduce the complex fin motions that fishes use for propulsion and maneuvering. Fish fins are remarkable propulsive devices and can serve as inspiration for designing the next generation of AUV control surfaces.