Artificial Muscle

Actuators

Summary

McKibben artificial muscles provide pneumatic linear actuation with a high strength-to-weight ratio and natural compliance. The actuator consists of an elastic cylindrical tube covered by an inelastic braided shell. Due to the weave-angle of the braided shell, increasing internal pressure causes the muscle to expand radially and contract longitudinally. This contraction provides a large force that can be used for robotic actuation. Based on a third-order dynamic model of the system, two adaptive position controllers are developed, proven stable using Lyapunov Theory, and tested experimentally. For comparison, a PID position controller is shown to be incapable of accurate tracking due to excessive vibration. An adaptive control scheme that estimates the actuator parameters yields excellent sine wave tracking up to 3 Hz. Compensation for the pressure dynamics using an adaptive backstepping controller ensures accurate tracking of a 4 Hz sine wave with increased amplitude.

Collaborators
 
Ian Walker, Clemson University

Bill Kier, University of North Carolina

Darren Dawson, Clemson University

Sponsor

NASA

Desired and actual displacement under adaptive backstepping control

For further information:  cdrahn@psu.edu. 

Copyright © 2001 Mechatronics Research Laboratory