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Proceedings Paper

Walking with springs
Author(s): Thomas G. Sugar; Kevin W. Hollander; Joseph K. Hitt
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Paper Abstract

Developing bionic ankles poses great challenges due to the large moment, power, and energy that are required at the ankle. Researchers have added springs in series with a motor to reduce the peak power and energy requirements of a robotic ankle. We developed a "robotic tendon" that reduces the peak power by altering the required motor speed. By changing the required speed, the spring acts as a "load variable transmission." If a simple motor/gearbox solution is used, one walking step would require 38.8J and a peak motor power of 257 W. Using an optimized robotic tendon, the energy required is 21.2 J and the peak motor power is reduced to 96.6 W. We show that adding a passive spring in parallel with the robotic tendon reduces peak loads but the power and energy increase. Adding a passive spring in series with the robotic tendon reduces the energy requirements. We have built a prosthetic ankle SPARKy, Spring Ankle with Regenerative Kinetics, that allows a user to walk forwards, backwards, ascend and descend stairs, walk up and down slopes as well as jog.

Paper Details

Date Published: 19 March 2011
PDF: 15 pages
Proc. SPIE 7976, Electroactive Polymer Actuators and Devices (EAPAD) 2011, 797602 (19 March 2011); doi: 10.1117/12.882214
Show Author Affiliations
Thomas G. Sugar, Arizona State Univ. (United States)
Kevin W. Hollander, SpringActive, Inc. (United States)
Joseph K. Hitt, United States Military Academy (United States)


Published in SPIE Proceedings Vol. 7976:
Electroactive Polymer Actuators and Devices (EAPAD) 2011
Yoseph Bar-Cohen; Federico Carpi, Editor(s)

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