New Design of a Soft Robotics Wearable Elbow Exoskeleton Based on Shape Memory Alloy Wire Actuators

Applied Bionics and Biomechanics, 2017 · DOI: https://doi.org/10.1155/2017/1605101 · Published: September 5, 2017

Assistive Technology Rehabilitation Biomechanics

Simple Explanation

This paper introduces a novel elbow exoskeleton for medical rehabilitation, utilizing shape memory alloy (SMA) wires for actuation. Unlike traditional exoskeletons with rigid components, this design uses a 3D-printed structure and SMA wires to achieve a lightweight and quiet operation. The SMA wires contract when heated, producing the arm movement directly, eliminating the need for pulleys. This design aims to improve comfort and portability for patients undergoing stroke rehabilitation. The exoskeleton's design incorporates a control system to manage the SMA wires' actuation, using a bilinear proportional-integral-derivative (BPID) controller. Flex sensors provide feedback on the elbow's angular position, allowing for precise control of the rehabilitation process.

Study Duration

Not specified

Participants

Male subject, 1.8 m height, 80kg, 23 years old

Evidence Level

Not specified

Key Findings

1
The developed SMA-actuated exoskeleton achieves a low weight of approximately 0.6 kg, enhancing comfort and portability for medical rehabilitation.
2
Experimental results demonstrate the feasibility of using SMA actuators for elbow flexion-extension, with a heating time response of 4.5 seconds and a cooling time of approximately 25 seconds.
3
The bilinear PID (BPID) control system effectively manages the SMA actuators, achieving a stationary state error of 3.42 degrees in positive step responses.

Research Summary

This research presents the design and preliminary results of a wearable elbow exoskeleton that utilizes shape memory alloy (SMA) wires for actuation. The device aims to address limitations of existing exoskeletons, such as high weight and noise, by employing a soft robotics approach. The exoskeleton incorporates a 3D-printed structure, SMA wire actuators, and a control system based on a bilinear PID controller. Experimental results demonstrate the feasibility of the design, showing promising performance in terms of weight, actuation, and control. The authors conclude that the SMA-actuated exoskeleton offers a viable solution for elbow medical rehabilitation, providing a comfortable, portable, and low-cost alternative to traditional devices. Future work will focus on improving the cooling process and further refining the control system.

Practical Implications

Improved Patient Comfort

The lightweight and quiet operation of the SMA-actuated exoskeleton can enhance patient comfort during rehabilitation sessions.

Enhanced Portability

The reduced weight and simplified design of the exoskeleton can improve portability, allowing patients to use the device in various settings.

Cost-Effective Rehabilitation

The use of low-cost materials and 3D printing can make the exoskeleton more accessible and affordable for patients and healthcare providers.

Study Limitations

1
The SMA materials have nonlinear behaviour due to the hysteresis phenomena
2
Low actuation frequency and limited bandwidth. It is inﬂuenced by SMA heating/cooling speed.
3
The cooling process is slower, almost 25 seconds.

Your Feedback

Was this summary helpful?

Back to Assistive Technology