An elastic pulsed-jet thruster for Soft Unmanned Underwater Vehicles

Abstract

Ahstract-This paper reports on the development of a new kind of unmanned underwater vehicle which draws inspiration from cephalopods both in terms of morphology and swimming routine. The robot developed here is the first in its kind, being a soft aquatic robot which travels in water by pulsed-jet propulsion. The general design principles of this innovative kind of underwater robot are illustrated and a first prototype is built and tested. The experiments demonstrate an inverse correlation between the frequency of pulsation and the speed of the robot. A mathematical model which associates the kinematics of the pulsating routine to the dynamics of the swimming is devised and compared with the experiments in order to better investigate the interplay of the various design parameters.

A Multi-soft-body Dynamic Model for Underwater Soft Robots

“…for as much as 80% in volume of rubber-like materials and capable of manipulating as well as travelling in the aquatic environment either via waterborne pulsed-jet propulsion or legged locomotion. The robot essentially consist of a central elastic shell, referred to here as the Soft Shell Mantle (SSM), which is designated to performing the pulsed-jet propulsion via the recursive ingestion and expulsion of finite slugs of ambient water [6,7]. From this central unit, a number of manipulators, i.e.…”

“…This vehicle has been tested both in controlled environments as well as in open water, see Fig. 2(b) and modeling and control of this complex system has been attempted by separately accounting for the various mechanical units [6,10]. Here, for the first time, the authors attempt to formulate a unified model which encompasses internal actuation and external dynamics.…”

“…, and 6 , where N(X) and M(X) are the internal force and torque vectors, respectively, while n(X) and m(X) are the external force and torque for unit of X. The screw inertia matrices are equal to: 6 .…”

“…, and 6 , where N(X) and M(X) are the internal force and torque vectors, respectively, while n(X) and m(X) are the external force and torque for unit of X. The screw inertia matrices are equal to: 6 . In the equations above ρ b and ρ s are the body densities, A(X) is the section area equal to A = πh 2 b , where h b (X) is the cross section radius, h s is the half of the shell thickness and J(X), I(X) are the second moment of inertia of the micro-solid equal to…”

Underwater soft-bodied pulsed-jet thrusters: Actuator modeling and performance profiling

“…Three prototypes (previously reported by Giorgio-Serchi et al (2013a,b,c) are employed here for the purpose of analyzing both the working routine of the actuator and the whole-body dynamics of the vehicles. These models have been reviewed below for the reader’s convenience.…”