Exploring the backward swimming ability of a robotic fish

Abstract

This article investigates the capability for backward swimming of a carangiform-fish-like robot with only three joints. A simple dynamic model based on a fixed point, a point in the body without perpendicular oscillation, is first developed to analyze the feasibility of backward motion for the robot. Through this theoretical analysis, we find that the fixed point lies closer to the robotic fish tail with higher backward swimming speeds. Combining the theoretical analysis with experimental optimization, we further explore backward swimming patterns using particle swarm optimization. After a series of online optimal experiments, we find several locomotion gaits that can make the robotic fish swim backward, and the corresponding fixed points are similarly located near the tail. The backward swimming velocity is strongly correlated with the fixed point position along the robotic fish body, which verifies the effectiveness of our fixed-point model.

Design of a Carangiform Swimming Robot through a Multiphysics Simulation Environment

“…3) are attached to the rigid bodies of the model; the zero index refers to the robot head, while non-zero indexes identify the tail links. Each body of the assembly, except the caudal fin, is approximated by a cylinder and is subjected to hydrodynamic forces coming from Equation (8). The propulsive forces and torque F T , F L , and M, are applied to the fin.…”

“…As stated in [1], the motion law generally adopted in modeling the tail undulation of carangiform swimmers is Lighthill's travelling wave [5], a harmonic function with an amplitude that increases towards the caudal fin and that describes the shape of the tail as a function of time. Several robotic fish prototypes propelled by carangiform locomotion have been manufactured in the past few decades [1,7,8]. In addition to the novel soft robotics design method [9], the most common solution consists of a rigid head hinged to a piecewise flexible tail driven by multijoint serial mechanisms.…”

Flow Characteristics of a Fish-Like Body Based on Taguchi Method under Different Strouhal Numbers

“…Moreover, the Taguchi method can also be used to investigate the infuence of various factors on the experimental results by means of the analysis of variance. Te infuence of four factors, namely, caudal fn lengthdiameter ratio, caudal fn stifness, oscillation frequency, and spring stifness, on the swimming velocity of the fsh-like body was analyzed by Li et al [28] through the Taguchi method. Two groups of results were obtained through 25 groups of experiments under orthogonal design.…”