Three-dimensional dynamic modelling of robotic fish: simulations and experiments

Abstract

This paper deals with a three-dimensional (3-D) dynamic model for a free-swimming, multi-link fish-like robot to predict the dynamic characteristics of an artificial fish system using the Schiehlen method in the context of multibody dynamics. The robotic fish, according to propulsive mechanisms employed by fish, propels itself using lateral oscillations and achieves a climb or descent manoeuvre exploiting a pair of pectoral fins. Mechanically, the robotic fish consists of a stiff head, a flexible rear body and an oscillating lunate caudal fin, which can essentially be viewed as an open, tree-like multibody system. The kinematic analysis is then integrated with hydrodynamic analysis on multiple moving elements to derive complete dynamic equations in a form suited for computer implementation as well as controller design. A variety of locomotion behaviours, through regulating parametric sets, can be reproduced. Numerical simulations and actual experiments on degenerative planar swimming and combined motions are finally compared, which partially demonstrate the effectiveness of the built model.