A Biologically Derived Pectoral Fin for Yaw Turn Manoeuvres

Jonah R Gottlieb,Christopher J Esposito,George V Lauder,James L Tangorra

doi:10.1155/2010/635280

Abstract

A bio-robotic fin has been developed that models the pectoral fin of the bluegill sunfish as the fish turned to avoid an obstacle. This work involved biological studies of the sunfish fin, the development of kinematic models of the motions of the fin's rays, CFD based predictions of the 3D forces and flows created by the fin, and the implementation of simplified models of the fin's kinematics and mechanical properties in a physical model. The resulting robotic fin produced the forces and flows that drove the manoeuvre and had a sufficiently high number of degrees of freedom to create a variety of non-biologically derived motions. The results indicate that for robotic fins to produce a level of performance on par with biological fins, both the kinematics and the mechanical properties of the biological fin must be modelled well.

Highlights

Pectoral fins are used by fish and aquatic animals to execute a wide variety of swimming manoeuvres
We described the development of a biorobotic fin that has the controllability, degree of freedom (DOF) and mechanical properties required to produce the motions, forces and flows of the sunfish pectoral fin during a yaw turn manoeuvre
This is due to the mechanical limitations of the bio-robotic fin; the angular displacement of the fin rays in the sweep direction was limited in order to simplify the construction of the fin base

Summary

Introduction

Pectoral fins are used by fish and aquatic animals to execute a wide variety of swimming manoeuvres. They can be used as rudders to control pitch during high speed swimming and to enhance low speed manoeuvrability (Drucker and Jensen 1996; Westneat 1996; Wilga and Lauder 1999, 2000, 2001; Lauder and Drucker 2004) and as flapping, high degree of freedom (DOF) propulsors to propel and manoeuvre the animal at low speeds (Lauder and Drucker 2004) Because of this versatility, the pectoral fin has served as a source of inspiration for a range of bio-robotic devices (Kato and Furushima 1996; Anderson and Chhabra 2002; Fish et al 2003; Tangorra et al 2006, 2008; Palmisano et al 2007; Gottlieb et al 2008). These paired fins are often used synchronously and made to repeat the same fin beat over and over to produce the cyclic forces required for steady swimming or hovering and made to execute completely different kinematics that, within a single fin beat, produce a drastic reorientation of the fish body

Results

Discussion

Conclusion