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Muscle Powered Exoskeleton Device version 4.0 A.M.P.E.D.

amped arm brace brace disability Exoskeleton

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This is a preliminary work in progress design for an open source 3D printable exoskeleton arm brace to assist the disabled to raise their arm. As someone with a form of muscular dystrophy called SMA, I have significant difficulty lifting my arms. Similar devices exist, but they are cost prohibitive for most people and not covered by insurance. I wanted to create an open source, inexpensive exoskeleton arm brace that utilizes both springs to offset arm weight and a motor to raise the individual's arm that would be free to download and modify. Design is specifically made for maximum adaptability for various size individuals.

Any help or suggestions greatly appreciated. I am an artist with some experience in computer programming...need electronics help, programming help, engineering help etc.

PICTURED VERS 3

http://darkrubymoon.blogspot.com/2021/10/amped-assistive-muscle-powered.html

https://youtu.be/KaHBj5Fuhcs

Thinking a bit more about it, maybe nature could serve as a template ... generally, with limbs, muscles are locate near the body and rely on sinews and levers to actuate the limbs. This is probably a good configuration to reduce mass and thus weight out on the limbs, on long lever arms, which in turn reduces rotational inertia and weight-induced moments.

Maybe you already tried this with your "pulley" approach, so please apologize if I'm pointing out something you've already covered :-)

By the way, I'd imagine that you might get even more feedback by repeating your post in some Thingiverse groups with greater number of members, such as:

Engineering: https://www.thingiverse.com/groups/engineering
Arduino: https://www.thingiverse.com/groups/arduino
Robots: https://www.thingiverse.com/groups/robots

Thank You so much! I apologize for the delayed reply. I really appreciate Your suggestions and advise.

I have been considering using either harmonic drive or cycloidal drive in my design. To be honest, I was a little intimidated by their complexity, and I decided to stick to the KISS principle as much as possible for my first build, but make everything modular for future upgrades and modifications. I am already contemplating leg brace design using these...but the need for me to build the arm brace in my case is a bit more urgent...so i set that aside for future development. I have also been looking into making artificial muscle with fishing line wrapped in conductive material which has both weight and strength advantages...but it is such a new technology i decided I could later replace the pulley strings with this to augment the strength. Am a little unsure of the speed for the artificial muscle and how to regulate fine motor control.

You must be on the same page as me when it comes to the idea of some way to lock and unlock the arm position. My current design has the pulley cord pull on a sortof ratchet to keep it from dropping back down as the motor stops. When the motor reverses, the ratchet releases. Am not sure this is the best method as this mechanism broke during my first print and already had to print a repair part. Unfortunately that design will not work for the shoulder. My current design instead utilizes the locking mechanism in a car safety belt...but it is complicated and i am doubtful it will work as intended as it does not follow the K.I.S.S. principal.

Quite an impressive project!

Since motor torque and weight are on your "next steps" list, maybe harmonic drives might be of interest to you. Here's an example: https://www.thingiverse.com/thing:5220737

With regard to the files you uploaded here, Thingiverse offers features to organize them in a much neater way ... if you click on "create" above, you can upload them again, fill out an online form with a bit of additional information about your design, and you'll have created a new "thing" entry in the database as a basis for future contributions and improvements by the community.

And thinking out of the box a bit, I just remembered a concept I learned about in a cyber surgery context ... a "robotic" arm that doesn't have motors, only brakes. It permits manipulation by humans, but applies the brakes to guard against movement to undesired positions.

Since I don't know about the specifics of SMA, I wonder if this concept would be useful for simplifying the design. If you have the remanent muscle strength to temporarily lift the arm, but the strength to hold it up for any length of time is lacking, the "braking only" concept might work.

(If the strength limit applies even to momentarily available strength, the concept would not be applicable.)

Harmonic Drive built into an off-the-shelf ball bearing