Prototyping of cylindrical structures made of helical artificial muscles

Abstract

Pneumatic artificial muscles have many advantages. They have high force mass ratio, high compliance and simple structures. Especially, the flexibility contributes to compose novel mechanisms. The flexibility of pneumatic artificial muscles releases us from the spatially strict design required for rigid mechanical elements: it could actualize compact mechanisms made of a fewer parts. Our research group developed a thin McKibben actuator. The thin McKibben actuators is more flexible than conventional McKibben actuators. Authors succeeded in manufacturing novel soft mechanisms that are made of only braided artificial muscles. We aim to establish a design method for these novel mechanisms. We already have fabricated a cylindrical mechanism made of helical muscles. In this paper, we report a geometric model for the cylindrical mechanism. We focus on only deformation of a side surface in the coordinate system of muscles to simulate the movements of the cylindrical mechanism. The movement was verified by an experiment, and besides, it was simulated successfully in the geometric model that was created. The deformation of height and radius directions changed according to muscles alignment.