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Feb 17 17 8:47 PM

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I am currently working on a design for a robotic prosthetic leg for a tortoise who had a rather nasty run in with a fox. This left him with just one full and functioning leg, along with two half legs and one completely missing. This has left him in a state that makes movement rather difficult and certainly uncomfortable for him.

For a long while I was trying to figure out how to attach the leg to him as he is still growing so the commonly applied solution for tortoises of epoxy isn't an option. I've now decided on a heat shaped 3D printed mesh that clips over the back of his shell making it easily removable but lightweight and strong.

Now I'm onto the leg itself. I'm thinking the best solution would be a 2 jointed leg. Now I am not new to the world of electronics but this is my first stab at any form of prosthetic and if anyone could provide some advice it would be much appreciated. If this goes well I'm hoping to start playing with my own designs for human prosthetics too.

The two main questions are, what to use to drive the joints, and how to actually control the motion itself.

For the joints, I guess the options are either servos or stepper motors. Now the leg needs to be very compact so whatever I use can't be massive but it needs a good bit of torque. He ways around 2kg in total.

Power and control board can be fitted to the shell mount so it is literally the motors/servos that need fitting to his leg.

As for how to control it, my two trains of thought were, either A, seeing if I can use muscle sensors to trigger movement when he tried to move his missing leg, or B, using accelerometers which sense when he tries to move forward or backwards and triggers s single cycle of motion in that direction.

Option A could pose many problems what with the scale of the project, the thick and scaley nature of a tortoises skin and the inability to actually train it to try using the leg.

B seems more straightforward but I'd be interested to hear your opinions.

Again, absolutely any help would be much appreciated. Thanks
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#1 [url]

Feb 20 17 10:11 PM

The only issue I'm seeing with having sensor powered prosthetic is the size of the sensor its self! Tortoises are really small, so trying to get a sensor of that size would be tricky. Might be more worthwhile going for a mechanical one to start, or maybe even a roller of sorts? There is an amazing vet in the UK (Supervet) who does prosthesis for animals, and I've seen him use a roller-type design before.
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Something a little more sophisticated could be cool! Because you're using electronics, you need to think about making them waterproof (I suppose he goes swimming every now and then?)

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#2 [url]

Feb 21 17 6:13 PM

Firstly can I say, a massive thanks for the reply. Really not been sure where to go for advice on this so any help is really appreciated!

Hmm, yeah the sensor is probably not the way to go with the tortoise. What do you think about my idea with using an accelerometer to gauge which direction the tortoise is trying to move then assist him?
As for water proofing, my idea was to have the robotic leg itself fitted with a quick release design, where a more basic wheel type attachment can be fitted when the leg is charging or when he is heading into less electronic friendly environments.

Because he currently only has one fully functional leg, I'm not sure a simple roller design is enough. He requires something that an actually assist in propelling him to fully take the strain out of moving about.

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#3 [url]

Feb 22 17 10:04 PM

That's absolutely fine! Anytime :) My mechanical knowledge isn't my best part, as I'm a software programmer and mainly focus on AI. The accelerometer could be a great idea, I'm just trying to think where all of this electronics would go (Maybe have a computer on all the time to do the processing and then relay commands back? You can get really small TCP-IP chips nowadays). Maybe someone else in the forum can help with the mechanical side of things. Have a look on google images to try and get ideas?

http://www.ndtv.com/offbeat/tortoise-attacked-by-mongoose-gets-prosthetic-wheels-in-chennai-zoo-1419946
http://www.fiboni.com/2014/01/a-tortoise-named-schildi-gets-saved-by-a-prosthetic-wheel/

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