Design and Computational Modeling of Fabric Soft Pneumatic Actuators for Wearable Assistive Devices

Pham Huy Nguyen,Wenlong Zhang

doi:10.1038/s41598-020-65003-2

Abstract

Assistive wearable soft robotic systems have recently made a surge in the field of biomedical robotics, as soft materials allow safe and transparent interactions between the users and devices. A recent interest in the field of soft pneumatic actuators (SPAs) has been the introduction of a new class of actuators called fabric soft pneumatic actuators (FSPAs). These actuators exploit the unique capabilities of different woven and knit textiles, including zero initial stiffness, full collapsibility, high power-to-weight ratio, puncture resistant, and high stretchability. By using 2D manufacturing methods we are able to create actuators that can extend, contract, twist, bend, and perform a combination of these motions in 3D space. This paper presents a comprehensive simulation and design tool for various types of FSPAs using finite element method (FEM) models. The FEM models are developed and experimentally validated, in order to capture the complex non-linear behavior of individual actuators optimized for free displacement and blocked force, applicable for wearable assistive tasks.

Highlights

These intrinsically soft robots have advantages over conventional rigid robots by being low-cost, lightweight, highly compliant, and inherently safe when interacting with the unknown environment and human body[2,6]
We explored the combination of various textiles to mechanically program actuators to perform different motion profiles, while still being lightweight, compliant, and safe
We introduced two main classes of versatile fabric-based soft pneumatic actuators, the woven non-stretch fabric actuators and the knit fabric reinforced textiles actuators

Summary

Introduction

These intrinsically soft robots have advantages over conventional rigid robots by being low-cost, lightweight, highly compliant, and inherently safe when interacting with the unknown environment and human body[2,6]. Soft fabric actuation has shown possibilities of utilizing fabric to generate movement and provide assistance[74]. The construction of these fabric actuators has been through either intrinsic or extrinsic modifications of the materials[74]. Extrinsically-modified fabric actuators, are fabricated by superficially attaching active materials on the surface of the substrate fabric, for example laminating thermoplastic polyurethane (TPU) material on the substrate fabric to create FSPAs73,74. This paradigm shift has lead to design of SPAs that are integrated with or hidden underneath the users’ clothes. On the other side of the spectrum, modeling of knit FSPAs are still in the nascent phase of development[8,9]

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Conclusion