Meeting Abstract

S5.7  Wednesday, Jan. 5  The Development of Biorobotic Models of Highly Deformable Fins and Fin Sensory Systems TANGORRA, James*; ESPOSITO, Chris; PHELAN, Chris; LAUDER, George; Drexel University; Drexel University; Drexel University; Harvard University tangorra@coe.drexel.edu

Bony fish swim with a level of agility that is unmatched in human-developed systems. This is due, in part, to the ability of the fish to carefully control hydrodynamic forces through the active modulation of the fins’ kinematics and mechanical properties. To better understand how fish produce and control forces, biorobotic models of the bluegill sunfish (Lepomis machrochirus) caudal fin, pectoral fin, and pectoral fin sensory system have been developed. The designs of these systems were based on detailed analyses of the anatomy, kinematics, and hydrodynamics of the biological fins. The fin models have been used to investigate how fin kinematics and mechanical properties influence propulsive forces, and the sensory system model has been used to investigate how mechanical and hydrodynamic information from the fin and its wake flow can be used as feedback for the closed loop control of the fin. Results from studies conducted with the fin models indicate that subtle changes to the kinematics and mechanical properties of fin rays can impact significantly the magnitude, direction, and time course of the 3d forces. The magnitude of the force tends to scale with stiffness, but the direction of the force is not invariant, and this causes disproportionate changes to the magnitudes of the thrust, lift, and lateral force components. Results from studies conducted with the sensory system model support the hypothesis that fin ray curvature, actuator force, and the pressure along the fish body capture time-varying characteristics of the propulsive force. However, none of the sensor modalities alone are sufficient to predict propulsive force. Knowledge of the time-varying force vector with sufficient detail for closed-loop control of a fin’s motion will result from integrating features from multiple sensor modalities.