Quasi-Static Continuum Model of Octopus-Like Soft Robot Arm Under Water Actuated by Twisted and Coiled Artificial Muscles (TCAMs)

TL;DR

This paper develops a quasi-static continuum model for an octopus-like soft robot arm actuated by lightweight, high-force artificial muscles, incorporating fluid forces and planar cross-section deformation to mimic biological behavior.

Contribution

It introduces a novel continuum model based on Cosserat theory that accounts for planar cross-section deformation and fluid interactions in underwater soft robots.

Findings

Model captures arm bending and deformation accurately.

Hydrostatic and dynamic fluid forces significantly influence arm motion.

Artificial muscles provide high force-to-weight ratio for soft actuation.

Abstract

The current work is a qualitative study that aims to explore the implementation of Twisted and Coiled Artificial Muscles (TCAMs) for actuating and replicating the bending motion of an octopus-like soft robot arm underwater. Additionally, it investigates the impact of hydrostatic and dynamic forces from steady-state fluid flow on the arm's motion. The artificial muscles are lightweight and low-cost actuators that generate a high power-to-weight ratio, producing tensile force up to 12,600 times their own weight, which is close to the functionality of biological muscles. The "extended" Cosserat theory of rods is employed to formulate a quasi-static continuum model of arm motion, where the arm's cross-section is not only capable of rigid rotation but also deforms within its plane. This planar deformation of the arm cross-section aligns with the biological behavior of the octopus arm, where the stiffness of the hydrostat is directly induced by the incompressibility of the tissues. In line with the main goal, a constitutive model is derived for the material of the octopus arm to capture its characteristic behavior.