Nonlinear Passive Cam Based Springs for Powered Ankle Prostheses

Abstract

This article studies the design of passive elastic elements to reduce the actuator requirements for powered ankle prostheses. The challenge is to achieve most of the typically nonlinear ankle response with the passive element so that the active ankletorque from the actuator can be small. The main contribution of this article is the design of a cambased lowerlimb prosthesis to achieve such a nonlinear ankle response. Results are presented to show that the addition of the cambased passive element can reduce the peak actuator torque requirement substantially, by ∼74%. Moreover, experimental results are presented to demonstrate that the cambased design can achieve a desired nonlinear response to within 10%.