Final Deliverables

Hey all,

Here’s the last post for a while. We scrambled together the system just in time for Olin Expo, though admittedly ran into some technical difficulties in the final product (turns out continuous rotation servos don’t substitute easily for your typical position control servos). Regardless, the circuit and the mechanism both work, and both have plenty of room for improvement.

Final_EMG_Schematic

POSS_FinalPaper

GrabCAD Repository

Above are the links to the major deliverables. The final paper details the entire system, including the most recent update to the mechanical system. The GrabCAD repository has the Solidworks models (if you want to edit or build on the design), the .STL’s (if you want to print your own), and the .x3g’s (if you happen to have some Makerbots). if you expand the “read more” tab at the bottom of this post, you’ll also find the text for the Makerware profile I used to print Ninjaflex and ABS simultaneously on the Makerbox 2X. Just paste that into a custom profile and you should be all set to print! (warning: Ninjaflex is very finicky. It will take a few tries and some patience to tune it to your printer)

Thank you all for following along on this project. It has been a great journey with lots of twists and turn. In the spirit of open source, we highly encourage you to modify and build upon this design.

Sincerely,

-The Prosthetic OSS Team

First Glance at Integration

This video shows our working EMG after one small edit from last time (updated circuit diagram shown below). We haven’t changed much between this post and our last one but we have these fun results so we thought we’d post the video. The finger used in the video is actually from several iterations ago. So, all in all, not much new content for this post but please enjoy the cool video and get excited for continued integration!

The resistor values in the low pass filter have been adjusted to lower the cut-off frequency. This sharpens the output and removes a lot of noise.

MIT Biomechatronics Group Visit

This past Friday, Meghan and Myles went to the MIT Media lab to visit the Biomechatronics group, which researches and develops some of the most advanced lower-limb prosthetics in the world. More specifically we were there to see David Hill, a graduate student and friend of one of our professors who kindly agreed to give us some of his time. While there, we also got to meet and speak with Luke Mooney, another graduate student in the Biomechatronics group. David is on the physics side and specializes in the dynamics of human locomotion to develop a human running model. Luke is a mechanical engineer who is designing a lower-leg exoskeleton.

Admittedly, we did not enter this conversation with many specific questions. We were there to absorb whatever information we could from people deeply involved in the field and to establish some initial contacts, and we were successful on both fronts. In short, we got some advice on the direction of our project. In our discussion, Luke suggested three potential roads that this project could go down:

1.) Socket Design. Sockets are apparently one of the most fundamental problems in prosthetics today. People’s bodies are neither rigid nor unchanging, yet most sockets are designed as though they were. The Media Lab is actually taking steps already to improve on that by designing custom 3D printed rubber sockets with varying hardness regions, providing both maximum support and comfort for the user.

2.) Reading “Intent.” This refers to the idea that, since we are working with hands, we need a channel through which the user can signal a desired action to the prosthetic. In our case, this refers to the circuit we are trying to develop to read the electrical pulse of muscle contractions from the skin. Other potential methods that have been tried for reading intent include EEG, mechanical control, and electrode arrays implanted in the brain.

3.) Device Design. This is what most people think of when they think of “prosthetic design.” It refers to the design and construction of the device itself. Luke and David suggested that, to avoid unwieldy complexity, we consider making specialized limbs for different tasks since these can be much cheaper and easier to make while still providing enormous benefit to the user.

Though our team is still waiting until tomorrow to re-unite and de-brief on how this visit will affect our direction, this advice gives us a much more solid bearing on what is possible from the view of experts in the field.

More to come soon,

-The Prosthetic OSS Team

A Long-Expected Journey

Hello, World!

We four engineering students (Meghan, Myles, Nitya, and Raagini) at Franklin W. Olin College of Engineering have been planning an adventure since mid-last year: building a robotic hand prosthetic. Inspired by everything from the E-nable project to MIT’s Biomechatronics lab, this Olin Self Study (OSS) wants to push forward the world of bionic prosthetics by exploring ways of reclaiming control of the muscles of the hand by reading signals from the body.

Over the course of the year we will be researching, testing, and prototyping our ideas and sharing them with you, the reader, via this blog. Expect weekly updates at the very least, interspersed with thoughts, revelations, complications, and more.

We would love to hear from you as well to prevent us from “engineering in a bubble.” Research thrives on dissent and morale leans on feedback, so please leave both in the form of comments, e-mails, etc. as you follow our blog!

Sincerely,

-The Prosthetic OSS