Date of Award

Spring 1-1-2013

Document Type


Degree Name

Master of Science (MS)


Mechanical Engineering

First Advisor

Schimmels, Joseph M.

Second Advisor

Huang, Shuguang

Third Advisor

Voglewede, Phillip A.


This thesis presents the design and test results of a passive prosthetic ankle that has mechanical behavior similar to that of a natural ankle. The ankle prosthesis is designed to store and return enough energy to the amputee to propel their body forward during push-off.

The ankle prosthesis is a 2 degree of freedom (DoF) mechanism containing a network of conventional compression springs. One DoF allows the lower leg to compress when weight is applied; the other allows the foot to rotate about the ankle joint. Bulk property and dynamic performance criteria are used to assess the performance of the ankle prosthesis. Lightweight, compactness and low friction are the primary bulk property requirements for the ankle device. Stiffness nonlinearity and active behavior similar to that of a human ankle are the major dynamic performance characteristics.

In this research, a preliminary computer geometric model of the prosthesis was developed, simulated, and refined in CAD software. A proof-of-concept prototype was then fabricated, modified and tested on both a robot and a human subject. The test results showed that the designed ankle prosthesis demonstrated its ability to satisfy the bulk property requirements and some of the dynamic performance characteristics. The nonlinearity of ankle stiffness was validated, however, more active behavior should be achieved by the prosthesis during push-off.