Structural dynamics of a pulsed-jet propulsion system for underwater soft robots

摘要

This paper entails the study of the pulsed-jet propulsion\udinspired by cephalopods in the frame of underwater\udbioinspired robotics. This propulsion routine involves a\udsequence of consecutive cycles of inflation and collapse of\udan elastic bladder, which, in the robotics artefact developed\udby the authors, is enabled by a cable-driven actuation of a\uddeformable shell composed of rubber-like materials. In the\udpresent work an all-comprehensive formulation is derived\udby resorting to a coupled approach that comprises of a\udmodel of the structural dynamics of the cephalopod-like\udelastic bladder and a model of the pulsed-jet thrust production.\udThe bladder, or mantle, is modelled by means of\udgeometrically exact, axisymmetric, nonlinear shell theory,\udwhich yields an accurate estimation of the forces involved\udin driving the deformation of the structure in water. By\udcoupling these results with those from a standard thrust\udmodel, the behaviour of the vehicle propelling itself in\udwater is derived. The constitutive laws of the shell are also\udexploited as control laws with the scope of replicating the\udmuscle activation routine observed in cephalopods. The\udmodel is employed to test various shapes, material properties\udand actuation routines of the mantle. The results are\udcompared in terms of speed performance in order to\udidentify suitable design guidelines. Altogether, the model\udis tested in more than 50 configurations, eventually\udproviding useful insight for the development of more\udadvanced vehicles and bringing evidence of its reliability\udin studying the dynamics of both man-made cephalopodinspired\udrobots and live specimens.