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robot "skin"

donkey

Feb 26, 2011
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hey people.
am hoping to get advice on an idea that I hope will act as both a "skin" and sensor for future robotics
sensormatt.png

sensormat1.png


so the pics are bad but I will run through the idea.
the black wire is the anode and is connected to a conductive sheet (most likely copper)
placed above it is a sheet with a good resistance value.
when you touch the top sheet the circuit to the 3 top wires (or four or however many you decide one) they calculate a rough circle(see the really rough circles I drew?) of where it "could" be connected to. a microcontroller then calculates the are that all these circles intercepts giving the rough location of the the connection.

I can think of a few uses for this but it has been a design that has been in my head for ages. the only issue I have is if you completely cover and object with this "skin" and can I keep them seperate AND allow them to make a closed circuit withouth and object getting in the way.
the other problem is what material would be best for the "skin"? it had to have an even resistive value to help the microcontroller identify the rough location.
I went against the touch screen technology as it does not locate pressure but infared (as far as I am aware) any help on this would be HUGELY appreciated

just thought of another issue, how can I make it so it won't act as a capacitor too?
 
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Raven Luni

Oct 15, 2011
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Interesting.

My first thought was why not make it more like a touch screen. As for not acting like a capacitor - I think that might actually be a better way to do it. Capacitive touch screens are more accurate as far as I'm aware.

If I was designing something like this, I would use 2 layers of conductive film separated by a thin sheet of rubber or foam (something with a good degree of elasticity). The conductive layers would act as capacitor plates and the capacitance would vary according to the pressure applied.

As for position, you would have to use a grid of these cells.
 

Raven Luni

Oct 15, 2011
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you could also stack a few layers like this connected in parallel if youre having trouble with sensitivity / responsiveness.
 

Raven Luni

Oct 15, 2011
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Another problem you might encounter is tightness and pressure around joints. Software is really the only way around this. You would need to train a neural net to recognise the difference between external contact and 'autoresponse'
 

donkey

Feb 26, 2011
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for your last response, could you train me on the difference first? lol
also if hepothetically this was to work is there a conductive layer that has properties similiar to skin, like a rubber? it is just a concept at this point but the possibilities are growing. for example if I do as you say and use it as a capacative screen then I could also get it to recognise tightness of grip on a robotic hand, it could self assess if there has been any tampering through a cut or removal of the skin.... the list grows bigger and bigger. but as I said... still just a concept
 

donkey

Feb 26, 2011
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hey just quickly how thing should the rubber be between layers? are we talking milimetres or nanometres? or something even smaller?
also I was thinking about joints and I have encountered what could be a problem if I use metal sheets. if I put it on a joint they will stretch and contract possibly breaking the plate. this is why I am after a conductive material that "stretches" even a little to allow for some give in joint areas
 
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