* Computer Interface For A Passive Self-Contained Microcomputer Controlled Above-Knee Prosthesis

Thesis (B.S.), Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1988. Includes bibliographical references.

By Erik J. Heels

First published 05/16/1988; MIT Dept. of Electrical Engineering and Computer Science; publisher: Massachusetts Institute of Technology.

[2015-02-03 – EJH added metadata, abstract, acknowledgment, and dedication for MIT thesis, about which he is still proud. The full text of this thesis is available online.]


            Author: Heels, Erik J. (Erik John)
       Citable URI: http://hdl.handle.net/1721.1/14584
Other Contributors: Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.
           Advisor: Woodie C. Flowers.
        Department: Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.
         Publisher: Massachusetts Institute of Technology
       Date Issued: 1988
          Keywords: Electrical Engineering and Computer Science.


The feasibility of a passive self-contained microcomputer controlled above-knee prosthesis has been demonstrated by past research. The three goals of this thesis were to revise the algorithm which controls the damping profile of the knee, to fix the low frequency discontinuous behavior of the knee, and to write the software for interfacing the entire unit with a Macintosh computer. The control algorithm is written in assembly language, and the limiting factor on its accuracy is the truncation of significant figures caused by mathematical manipulation of digital data. The low frequency discontinuous behavior demonstrated by the knee was partially caused by inaccurate analog differentiation. The computer interface for the Macintosh computer is very simple and easily modifiable to future control algorithms. The algorithm itself can easily be modified by adding additional hardware to the design such as torque transducers. As it now stands, no knowledge of computers is necessary for a therapist to interactively change the parameters of the control algorithm.


First and foremost, thank you Mom and Dad for your prayers, your constant support and worrying, and your unwavering faith in me. Do you remember when I swore I’d never buy a computer? My, how things have changed.

Thank you Woodie for introducing me to this project and for telling me that I could do it. Thank you Bill Murray for the use of your personal lab equipment and for helping me in the lab. Thank you Ted for showing me the inside of a Macintosh. Thank you Ed, Mike, and Leslie for your constant support around the dorm. Thank you Dave and Dave, without whom I never would have graduated from M.I.T. in four years. Thank you Peter for helping me print out this thesis.

Finally, I owe a special thank you to Karl Lindstrom, who worked on this project last year. Thank you for flying out from California to help me, for the many long distance phone calls, and for many late nights with David Letterknee. Karl, you warned me that this project would get me as it got you. You told me it would wrap me up body and soul, that it would dominate my every waking thought. Indeed it has, but it has been well worth it. And Karl, I think you can take care of plants.


To my great, great, great grandfather, James Heels, who brought my family to this continent in 1841, and who later lost his foot to a bone disease.

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Erik J. Heels is a patent and trademark lawyer for Boston startups, Red Sox fan, MIT engineer, and musician. He blogs about technology, law, baseball, and rock ‘n’ roll at erikjheels.com.

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One Reply to “* Computer Interface For A Passive Self-Contained Microcomputer Controlled Above-Knee Prosthesis”

  1. An impressive share! I have just forwarded this onto a colleague who
    wwas doing a little homework on this. And he actually ordered
    me breakfast duee too the fact that I stumbled upon it for him…
    lol. So allow me to reword this…. Thanks for the meal!!

    But yeah, thanx for spending some time to discuss this topic here on your blog.

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