A Self-sensing Inverse Pneumatic Artificial Muscle

Abstract

In recent years, the inverse pneumatic artificial muscles attained great attention in soft robotics, especially for the wider motion range compared to traditional positive pneumatic actuators. Besides self-sensing is a recognized highly desirable property for soft actuators to enable proprioception and to facilitate the soft robots control, a self-sensing strategy for a soft inverse pneumatic muscle was still missing. In this paper, we present the first self-sensing inverse pneumatic artificial muscle in which the reinforcing but compliant element that guides the actuator motion during actuation has not only a mechanical function but, being also electrically conductive, it endows the actuator with self-sensing. Here, the actuator design and manufacturing are described, together with an electromechanical characterization. In addition, we demonstrate its self-sensing capability in a dynamic setting, by predicting the actuator strain from its electric resistance variation, through a calibration model.

How to Easily Make Self-Sensing Pneumatic Inverse Artificial Muscles

“…On the other hand, the location of the sensor might be changed. Whilst in this study it was arranged coaxially with the actuator (with the intended advantages described in the Introduction), in [ 33 ] it was inserted inside the constraining coil, which was made soft on purpose. Different strategies might also be possible.…”

“…Soft pneumatic actuators can also be designed in such a way that, upon pressurisation, they elongate instead of contracting; in this case, they are often referred to as ‘inverse artificial muscles’. An efficient configuration to achieve this effect is represented by an elastomeric inflatable tube surrounded by a plastic coil, which restricts radial expansions upon inflation, enabling only elongations [ 28 , 29 ]. Planar and textile-compatible versions of this concept have also been demonstrated, by radially constraining fluidically driven small elastomeric tubes via a surrounding fabric, which can integrate the tubes in various ways [ 30 , 31 , 32 ].…”

“…Here, we present a preliminary investigation aimed at endowing coil-based inverse artificial muscles with self-sensing ability, while maintaining ease of fabrication, especially with off-the-shelf materials and low-cost processes. To the best of our knowledge, so far only one paper has presented a self-sensing version of coil-based inverse artificial muscles: a piezoresistive sensor was created by making the coil as an insulated elastomeric conductive cord, such that it had not only a mechanical function (constraining of radial strains) but also an electrical function [ 33 ].…”

Soft Pneumatic Muscles: Revolutionizing Human Assistive Devices with Geometric Design and Intelligent Control

“…A seminal study [ 7 , 8 ] presents a significant advancement in pneumatic actuation, introducing the development of the first self-sensing inverse pneumatic artificial muscle. This groundbreaking actuator surpasses the capabilities of conventional positive pneumatic actuators by offering an expanded range of motion.…”

The Research on Soft Pneumatic Actuators in Italy: Design Solutions and Applications

“…A similar approach is also employed by Lorenzon et al [54]. The authors developed an actuator consisting of a cylindrical inflatable chamber, two heads, and a reinforcement structure.…”