In-situ sensing and dynamics predictions for electrothermally-actuated soft robot limbs
Date
2022
Authors
Sabelhaus, Andrew P.
Mehta, Rohan K.
Wertz, Anthony T.
Majidi, Carmel
Version
Published version
OA Version
Citation
A.P. Sabelhaus, R.K. Mehta, A.T. Wertz, C. Majidi. 2022. "In-Situ Sensing and Dynamics Predictions for Electrothermally-Actuated Soft Robot Limbs." Frontiers in Robotics and AI, Volume 9, pp.888261-. https://doi.org/10.3389/frobt.2022.888261
Abstract
Untethered soft robots that locomote using electrothermally-responsive materials like shape memory alloy (SMA) face challenging design constraints for sensing actuator states. At the same time, modeling of actuator behaviors faces steep challenges, even with available sensor data, due to complex electrical-thermal-mechanical interactions and hysteresis. This article proposes a framework for in-situ sensing and dynamics modeling of actuator states, particularly temperature of SMA wires, which is used to predict robot motions. A planar soft limb is developed, actuated by a pair of SMA coils, that includes compact and robust sensors for temperature and angular deflection. Data from these sensors are used to train a neural network-based on the long short-term memory (LSTM) architecture to model both unidirectional (single SMA) and bidirectional (both SMAs) motion. Predictions from the model demonstrate that data from the temperature sensor, combined with control inputs, allow for dynamics predictions over extraordinarily long open-loop timescales (10 min) with little drift. Prediction errors are on the order of the soft deflection sensor's accuracy. This architecture allows for compact designs of electrothermally-actuated soft robots that include sensing sufficient for motion predictions, helping to bring these robots into practical application.
Description
License
Copyright © 2022 Sabelhaus, Mehta, Wertz 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.