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. 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. When the passive stretch ratio of the proposed actuator reaches 30%, the blocking force at -25 kPa changes from 60 to 68 N. Removing 0.6 N caused by spring tension, the blocking force increases by nearly 12%. For the same passive stretch ratio, the maximum contraction ratio increases from 0.7 to 0.77 with an improvement of 10%. We believe that the proposed artificial muscle will provide more inspiration to the robotics community, such as the ability to perform antagonistic actuations and adapt to complex actuation requirements.

Theoretical study of vacuum-powered artificial muscles with inner support and flexible skin

“…Artificial muscles have always been the focus of robotic research because of their widely applications in soft robots [1], bionic robots [2], wearable devices [3] and medical instruments [4]. In the past few years, vacuumpowered artificial muscles with inner support and flexible skin (VPAMs) have demonstrated great potential due to their promising mechanical properties such as fail-safe, compactness, robustness, high output stress and strain and fast response [5][6][7][8]. The key components of these artificial muscles consist of an internal support and a flexible skin.…”

Experimental investigation on enhancement in pure axial deformation of soft pneumatic actuator (SPA) with cap ring reinforcement

“…Fluid-powered fibre-reinforced actuators [21] have been devised, mirroring the intricate movements of the index finger and thumb. Numerous researchers [22][23][24][25][26][27][28][29][30][31][32][33][34][35] have made significant contributions in various areas, showcasing their remarkable work.…”