A Muscle-First, Electromechanical Hybrid Gait Restoration System in People With Spinal Cord Injury

Frontiers in Robotics and AI, 2021 · DOI: 10.3389/frobt.2021.645588 · Published: April 27, 2021

Spinal Cord Injury Assistive Technology Biomedical

Simple Explanation

This paper describes the development of a hybrid system designed to aid people with spinal cord injuries (SCI) in regaining their ability to walk. The system combines functional electrical stimulation (FES) to activate paralyzed muscles, a powered exoskeleton to provide assistance, and a control system to coordinate both. The design philosophy centers around a 'muscle-first' approach, where the individual's own muscles are the primary drivers of joint movement, with the exoskeleton providing supplementary power. This approach led to the development of efficient actuators and a burst-torque control system. The hybrid system was tested on two participants with SCI. The results showed that the addition of torque bursts increased gait speed. The system met the initial design requirements.

Study Duration

Not specified

Participants

Two participants with spinal cord injury

Evidence Level

Not specified

Key Findings

1
The addition of torque burst assistance from the exoskeleton resulted in an increase in gait speed for both SCI participants compared to passive or friction compensation modes.
2
Eliminating passive resistance in the exoskeleton joints alone did not significantly improve gait speed.
3
The study suggests that while the developed exoskeleton meets initial design specifications, further development is needed to ensure safe operating parameters, particularly regarding motor current at higher gait speeds.

Research Summary

This study presents a hybrid gait restoration system for individuals with SCI, combining implanted neural stimulation and a powered exoskeleton. The system uses a muscle-first approach, where the exoskeleton assists muscle-driven movements. The system's design focuses on low passive resistance actuators and a feed-forward torque controller. Testing with two participants showed that torque burst assistance from the exoskeleton improved gait speed. The findings suggest the potential of hybrid systems to restore gait in SCI, but also highlight the need for further optimization of control strategies and power management to ensure safety and efficiency.

Practical Implications

Rehabilitation Strategy

Muscle-first hybrid systems can leverage patient's own muscle activity, potentially improving muscle tone, blood flow, and overall health benefits compared to exoskeleton-only approaches.

Exoskeleton Design

Low passive resistance actuators are crucial for effective muscle-first control in hybrid exoskeletons, enabling the user's muscles to drive the joints with minimal resistance.

Control System Development

Advanced control strategies, such as torque bursting, can significantly enhance gait speed in hybrid systems, but require careful tuning and power management to avoid exceeding motor capabilities.

Study Limitations

1
The study involved only two participants, limiting the generalizability of the results.
2
Walk trials were short (10 m), potentially not fully capturing the system's performance over longer distances and with varying terrain.
3
Limited feedback implementation and lack of fatigue detection and compensation constrain long-term testing and real-world application.

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