Pneumatic muscle actuator (PMA) task-specific resistance for potential use in microgravity exercise

Area of Science:

• Robotics and Control Systems
• Biomedical Engineering
• Human Physiology

Background:

• Pneumatic muscle actuators (PMAs) offer a high power-to-weight ratio and are suitable for human interaction.
• PMAs exhibit nonlinear dynamics, making precise control challenging.
• Controlled PMAs can provide task-specific resistance for strength training, crucial for mitigating muscle atrophy in environments like spaceflight.

Purpose of the Study:

• To develop and evaluate a control system for a PMA to provide task-specific resistance during simulated isokinetic strength training.
• To assess the PMA's ability to mimic human muscle resistance and joint movement.

Main Methods:

• An open-loop control strategy utilizing a three-element phenomenological inverse model was implemented for PMA control.
• A motor was employed to simulate human quadriceps function, generating resistance against the PMA.

Main Results:

• The PMA control system achieved resistance and displacement tracking errors (RMSE) between 0.36-1.61 Nm and 0.55-1.59 mm, respectively.
• Simulated joint angle tracking errors ranged from 0.47 to 2.82 degrees.
• Successful simulation of isokinetic movement was demonstrated, with limitations noted for more complex resistance profiles.

Conclusions:

• The developed inverse model control system effectively generates task-specific resistance and displacement using PMAs.
• Closed-loop motor control is essential for accurately simulating complex isokinetic movements.
• Further advancements in PMA control and human simulation are needed for real-world human operator applications.