Passive Ankle-Foot Prosthesis Prototype with Extended Push-Off

Current commercially available prosthetic feet have
succeeded in decreasing the metabolic cost and increasing
the speed of walking compared to walking with
conventional, mostly solid prosthetic feet. However, there is
still a large discrepancy when compared with a non?disabled
gait, and the walking pattern remains strongly disturbed.
During the stance phase of the leg, these prostheses store
and return energy using a spring element. This spring
returns to its neutral position, which generates a push?off,
but the foot extends much less than with a non?disabled gait.
The walking pattern may improve with a more extended
push?off. In this paper, we present a passive ankle?foot
prosthesis that aims to deliver an extended ankle push?off
using a specific planetary gearbox arrangement and locking
mechanisms in order to release the energy in the spring over
the full natural stretching of the ankle. In recent years, both
powered and passive prosthetic devices have been
developed. The prosthetic foot presented in this paper is a
passive system, such that it has the possibility to be made
lighter and more robust than, for example, one driven by an
electric motor. Preliminary walking experiments were
conducted with a transfemoral amputee.