Modeling and Optimization of a Wire-Driven Carangiform Robotic Fish

Abstract

It is a great challenge to reproduce the tail swinging properties of fish to improve the maneuverability and propulsion of robotic fish. Inspired by the excellent swimming ability of carangiform fish, this study proposes an optimization method for wire-driven robotic fish to accurately imitate its oscillation characteristics to improve swimming performance. First, the robotic fish was designed using elastic tailbones and rigid joint plates via a wire-driven method. Then, kinematic and hydrodynamic models were developed using the Euler–Bernoulli beam theory and the elongated-body theory, respectively, to characterize tail deformation and propulsion performance. Moreover, the spacing of the tail joints was optimized to approach the swing curve of carangiform fish, resulting in an optimal configuration. Finally, three different robotic fish prototypes were fabricated and experimentally tested. The results show that the straight-line swimming speed, turning speed, and turning radius of the robotic fish with optimal non-uniform tail joint spacing are improved by 17.60%, 61.01%, and 26.64%, respectively, compared with the uniform joint spacing design. Moreover, the robotic fish achieved a maximum turning speed of $51.43^\circ /s$ and a minimum turning radius of 0.125 BL by using the modulated swing amplitude control method, significantly outperforming the other two configurations.