Arm-free paraplegic standing--Part I: Control model synthesis and simulation

Area of Science:

• Biomedical Engineering
• Neurorehabilitation
• Robotics

Background:

• Paraplegia often results in the loss of independent standing ability.
• Existing methods for paraplegic standing may require external support or extensive equipment.
• Utilizing residual upper body control offers a potential pathway for enhanced mobility.

Purpose of the Study:

• To investigate the feasibility of arm-free paraplegic standing.
• To propose a novel control strategy leveraging residual abilities and artificial stiffness.
• To analyze the stability and disturbance rejection capabilities of the proposed system.

Main Methods:

• Development of a control strategy using voluntary and reflex upper body activity.
• Application of functional electrical stimulation (FES) for knee and hip extension.
• Modeling and simulation using a closed-loop double inverted pendulum model with neural delays and trunk dynamics.
• Analysis of disturbance rejection under various ankle stiffness levels and biomechanical constraints.

Main Results:

• A linearized model indicated stability is achievable with appropriate ankle stiffness.
• Simulations demonstrated effective disturbance rejection strategies.
• Foot length was identified as a critical constraint for balancing, more so than trunk muscle strength.
• Ankle stiffness around 10 Nm/degree was found to be sufficient for stable arm-free standing.

Conclusions:

• The proposed control strategy shows promise for enabling arm-free paraplegic standing.
• Optimized ankle stiffness and consideration of foot length are crucial for successful implementation.
• This research contributes to advancing assistive technologies for individuals with spinal cord injuries.