Abstract

INTRODUCTION
A pneumatic muscle actuator (PMA) is a device that mimics the behavior of skeletal muscle by contracting and generating force when activated. This type of actuator has a high power to weight ratio and unique characteristics which make it ideal for human interaction. PMAs, however, are difficult to control due to nonlinear dynamics. Our objective was to control a PMA as a source of task-specific resistance in simulated isokinetic strength training. Task-specific resistance will benefit those in need of strength training through a joint's range of motion, including astronauts who need to counteract muscle atrophy during prolonged spaceflight. The lightweight, clean, and compact PMA driven by pressurized air is able to produce resistance in microgravity.
METHODS
An open-loop control method based on a three-element phenomenological inverse model was developed to control the PMA. A motor was simultaneously controlled to act as simulated human quadriceps working against the PMA-produced resistance.
RESULTS
For ankle weight replacement resistance profiles, the PMA control method produced resistance and PMA displacement tracking errors (RMSE) of 0.36-1.61 Nm and 0.55-1.59 mm, respectively. Motor position (simulated joint angle) tracking errors ranged from 0.47 to 2.82 degrees.
DISCUSSION
Results indicate that the inverse model based control system produces task-specific PMA resistance and displacement. Closed-loop motor control was able to simulate isokinetic movement successfully. More complicated resistance profiles reveal the need for closed-loop control. Future work focuses on advancing both the PMA control strategies and the capabilities of the human simulator so that actual human operator applications can be realized.

Authors

Hall KL, Phillips CA, Reynolds DB, Mohler SR, Neidhard-Doll AT

Institution

Wright State University, Dayton, OH, USA.

Source

Aviation, space, and environmental medicine 83:7 2012 Jul pg 696-701

MeSH

Biomimetic Materials
Equipment Design
Exercise
Humans
Leg
Materials Testing
Muscle Contraction
Muscle, Skeletal
Resistance Training
Task Performance and Analysis
Torque
Weightlessness

Pub Type(s)

Journal Article

Language

eng

PubMed ID

22779314