Highly Stretchable Polymer Optical Fiber for Mechanical Sensing in Artificial Tendons: Towards Novel Sensors for Soft Robotics

Arnaldo G Leal-Junior,Carlos Marques,Wagner Coimbra,Anselmo Frizera

doi:10.3390/act9040125

Arnaldo G Leal-Junior, Carlos Marques + Show 2 more

Open Access

https://doi.org/10.3390/act9040125

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Abstract

The control of tendon-driven actuators is mainly affected by the tendon behavior under stress or strain. The measurement of these parameters on artificial tendons brings benefits on the control and novel approaches for soft robotics actuators. This paper presents the development of polymer optical fiber sensors fabricated through the light spinning polymerization process (LPS-POF) in artificial tendons. This fiber has exceptionally low Young’s modulus and high strain limits, suitable for sensing applications in soft structures. Two different configurations are tested, indicating the possibility of measuring strain and stress applied in the tendon with determination coefficients of 0.996 and 0.994, respectively.

Highlights

The continuous evolution of robotics in conjunction with novel techniques for signal processing, control and instrumentation of robots have enabled the widespread of such devices in many applications [1,2]
The tensile tests were performed on thermoplastic polyurethane (TPU) and the LPS-polymer optical fibers (POFs), where the same strain rate was applied at all tests
The tendon and optical fibers characterizations were performed in a tensile test machine, where each material and their combinations with the TPU were analyzed

Summary

Introduction

The continuous evolution of robotics in conjunction with novel techniques for signal processing, control and instrumentation of robots have enabled the widespread of such devices in many applications [1,2]. Among many soft robot actuation technologies, as summarized in [3], tendon-driven actuators are remotely actuated and can lead to a soft robot for continuous operation with low stiffness [3], making it suitable in different applications [4,5,6], including minimally invasive surgeries [7] Such technology enables an optimized mass distribution in conjunction with the possibilities of developing underactuated robotic structures [8,9] as well as devices with configurable stiffness [10]. Some methods were proposed for ex-vivo such as imaging methods and stress-strain tests with universal testing machines [15] Both approaches are not able to provide real time measurements in non-structured environments or during the robot operation

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Results

Conclusion