Shape memory alloy (SMA) curator with embedded liquid metal curvature sensor for closed-loop control
Date
2021
Authors
Ren, Zhijian
Zarepoor, Masoud
Huang, Xiaonan
Sabelhaus, Andrew P.
Majidi, Carmel
Version
Published version
OA Version
Citation
Z. Ren, M. Zarepoor, X. Huang, A.P. Sabelhaus, C. Majidi. 2021. "Shape Memory Alloy (SMA) Actuator With Embedded Liquid Metal Curvature Sensor for Closed-Loop Control." Frontiers in Robotics and AI, Volume 8, pp.599650-. https://doi.org/10.3389/frobt.2021.599650
Abstract
We introduce a soft robot actuator composed of a pre-stressed elastomer film embedded with shape memory alloy (SMA) and a liquid metal (LM) curvature sensor. SMA-based actuators are commonly used as electrically-powered limbs to enable walking, crawling, and swimming of soft robots. However, they are susceptible to overheating and long-term degradation if they are electrically stimulated before they have time to mechanically recover from their previous activation cycle. Here, we address this by embedding the soft actuator with a capacitive LM sensor capable of measuring bending curvature. The soft sensor is thin and elastic and can track curvature changes without significantly altering the natural mechanical properties of the soft actuator. We show that the sensor can be incorporated into a closed-loop "bang-bang" controller to ensure that the actuator fully relaxes to its natural curvature before the next activation cycle. In this way, the activation frequency of the actuator can be dynamically adapted for continuous, cyclic actuation. Moreover, in the special case of slower, low power actuation, we can use the embedded curvature sensor as feedback for achieving partial actuation and limiting the amount of curvature change.
Description
License
Copyright © 2021 Ren, Zarepoor, Huang, Sabelhaus and Majidi. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.