Soft Exoskeletons
University of Illinois at Urbana-Champaign
FREE Architectures for Exoskeletons
Their innate compliance and low weight make FREEs well-suited for use in exoskeletons. These wearable devices can be used to restore or augment lost mobility in a medical application or improve lifting and carrying capacity and reduce risk of injury in an industrial setting.
FREEs’ output force and displacement can be tailored to a given application by arranging them in different architectures. The two studies on this page explored the performance of novel FREE architectures in exoskeleton applications.
Linear FREEs can be arranged (a) in parallel or (b) in two-level nested architectures for amplified contraction.
Elbow Exoskeleton
The goal of this work was to develop compact architectures of small-diameter FREEs for a compliant sleeve to provide torque to the elbow for assisted carrying and lifting.
Helical FREE architectures conformed to the shape of the arm at any joint angle for stiffness modulation. A linear architecture mimicked a human bicep, producing angular displacement in flexion by generating a contracting force. We evaluated the two architectures by measuring joint stiffness and angular displacement under different actuation and loading configurations.
Shoulder Exoskeleton
This study evaluated the feasibility of two different FREE architectures for a cable-driven exoskeleton, designed to reduce shoulder joint and muscle loads.
A nested FREE architecture used multiple contracting FREEs connected in series and in parallel to improve the stroke and force output compared to equal-length parallel actuators. A pennate architecture, inspired by the bipennate fiber arrangement in some biological muscles, consisted of symmetrical arrangements of FREEs at an angle of inclination from the horizontal, joined at a vertical centerline and fixed at their lateral ends.
(a) Nested linear and (b) pennate FREE architectures considered for the shoulder exoskeleton.
Learn more:
N. Thompson, X. Zhang, F. Ayala, E. T. Hsiao-Wecksler, and G. Krishnan, “Augmented Joint Stiffness and Actuation Using Architectures of Soft Pneumatic Actuators,” in Proceedings - IEEE International Conference on Robotics and Automation, 2018, vol. 5, pp. 1533–1538. Link
N. Thompson, A. Sinha, and G. Krishnan, “Characterizing architectures of soft pneumatic actuators for a cable-driven shoulder exoskeleton,” in Proceedings - IEEE International Conference on Robotics and Automation, 2019, vol. 2019-May, pp. 570–576. Link