An experimental study of the wire-driven compliant robotic fish

Abstract

Inspired by the live fish in nature, a robotic fish is built with a rigid anterior body and a wire-driven flexible tail. The flexible tail is comprised of skeleton segments and an elastic beam, while a rigid caudal fin is fixed at the posterior end of the beam to realize compliant flapping. In this study, comprehensive experiments are implemented to evaluate the swimming performance of this wire-driven robotic fish. The straight and turning swimming velocities, the consumed time of oriented direction swimming, the amplitude of swing angle and the lateral displacement of fishtail during cruising are measured. In order to estimate the straight swimming performance of the robotic fish, the Elongated-Body Theory of Lighthill combined with the experimental results is used to model the wire-driven compliant robotic fish. An experimental approach is proposed to estimate the swimming velocity and the deflection of compliant wire-driven robotic fishtail. The optimized model describes the flapping amplitude attenuation tendency, resolves the overestimation of cruising velocity in straight swimming and is capable to predict the straight average velocity accurately. Its feasibility is validated against the experimental data and a good match is achieved.