Integrated Temperature and Position Sensors in a Shape-Memory Driven Soft Actuator for Closed-Loop Control

Johannes Mersch,Gerald Gerlach,Carlos Alberto Gomez Cuaran,Mathis Bruns,Najmeh Keshtkar,Klaus Röbenack,Andreas Nocke,Chokri Cherif,Henriette Grellmann

doi:10.3390/ma15020520

Abstract

Soft actuators are a promising option for the advancing fields of human-machine interaction and dexterous robots in complex environments. Shape memory alloy wire actuators can be integrated into fiber rubber composites for highly deformable structures. For autonomous, closed-loop control of such systems, additional integrated sensors are necessary. In this work, a soft actuator is presented that incorporates fiber-based actuators and sensors to monitor both deformation and temperature. The soft actuator showed considerable deformation around two solid body joints, which was then compared to the sensor signals, and their correlation was analyzed. Both, the actuator as well as the sensor materials were processed by braiding and tailored fiber placement before molding with silicone rubber. Finally, the novel fiber-rubber composite material was used to implement closed-loop control of the actuator with a maximum error of 0.5°.

Highlights

Soft robotics research and industry application have been and likely will be expanding over the years [1]
Nerve fibers and muscle fibers correspond to the integrated sensors and actuators in soft robotic structures, respectively [4]
A soft actuator was presented that is based on a novel fiber-rubber composite material

Summary

Introduction

Soft robotics research and industry application have been and likely will be expanding over the years [1] These soft robots offer advantages compared to usual rigid robots in their versatility, adaptability and resilience. Structures used in the field consist of soft materials, mainly elastomers, in combination with actuator materials [2]. These elastomers can be reinforced by textiles, which may possess a higher stiffness in the fiber direction, but are still highly flexible. Such fiber-rubber composites are similar to systems found in nature like the combination of tendon fibers in soft tissue. The reinforcement textile can be employed as stabilization to restrict unwanted motion patterns or may be equipped with electroactive [5] or thermoactive [6] actuator fibers to enhance their functionality

Methods

Results

Conclusion