Passively stretchable vacuum-powered artificial muscle with variable stiffness skin

Abstract

A passively stretchable vacuum-powered artificial muscle (VPAM) is proposed in this work that extends the deformation mode of the existing VPAM, allowing it to have passively stretchable properties while maintaining the performance benefits. The passively stretchable VPAM is made possible by a new variable stiffness skin consisting of two composite layers. Each composite layer is divided into two parts: a non-stretchable part and a stretchable part. When vacuum pressure is applied, the composite layers are jammed and the skin becomes non-stretchable. Conversely, in the absence of pressure, the skin becomes stretchable, making the VPAM stretchable. The behaviour of the actuator has been theoretically modelled and the corresponding experiments have been carried out. Since the behaviour of the actuator with the skin in jammed state is consistent with that of the existing VPAM, the effect of passive tensile deformation on the behaviour of this type of VPAM is primarily analyzed. It is shown that the passively stretchable properties not only make the VPAM more similar to the deformation behaviour of biological muscles, but also enable the regulation of the blocked force and maximum contraction rate of the VPAM. We believe that the proposed artificial muscle will contribute to new robotic systems and provide more inspiration to the robotics community.