About Robot Hands And Human Bones

about robot hands and human bones

Everybody has seen the picture, right? ↑ It's by AstroMonster312 from twitter btw

First I thought: "Why in the world does Sun have such hands..? Giant thumb and pinky, elongated bottom phalanges?". I thought it was an odd design decision.

Yesterday I wanted to draw DCA with a certain hand pose, made the pose with my own hand and went: "wait a minute... human hands are squishy"

excellent job, Sherlock

Plenty things that we can do are tied to our thumbs that change their positions under the skin and are parts of our palms, all while the attendant has metal and plastic nonflexible palms.

Was he given biblically accurate human hand proportions, his fine motor skills wouldn't be so, ehm... fine.

He wouldn't be able to connect his thumb and pinky, barely would be able to connect ring finger and thumb.

Thumb movements in general would be very restricted and you know how much of a loss that would be.

Our hand looks like this:

well, approximately

to keep fine motor skills (which are crucial for for someone who's assigned to daycare) designers did this:

what exactly did they do?

Well, imagine your thumb was cut off (bottom segment that is a part of your palm included) and placed where it originally started (aka the second segment joint)

What does it give? It saves the opposed finger function (still think they could place some hinges inside his palm and it would work beautifully) as now the thumb has wider range of rotation

Made the pinky longer

Probably as a part of solving the inability to connect thumb with pinky problem. Or maybe they decided that short fingers are useless. Or accidentally made another ring fingers instead of pinkies and just installed them (I don't understand if they're the same length or pinkie is slightly shorter)

Made the top segments longer than ours (comparing by proportions. And for further when I say "bigger/shorter than humans' I mean the proportion). DCA's top segments are bigger than middle ones

For, uhm, reasons..?

Overall this makes an odd compromise between trying to keep the design human accurate and failing and making decisions that would just serve their function

More thoughts under the cut because the post is getting inexcusably long (and also a version of DCA hand but it's just broken human hand skeleton with a floating thumb, for it looks so dumb that it's even a bit funny)

^ the broken hand

Funfact: our thumbs (with the bottom segment taken in account) are slightly longer than our middle fingers.

DCA's fingers came to the same ratio but they got there the hard way:

Thumb was made bigger than humans' and the tips of fingers were also made bigger as I've mentioned before and thus the ratio was achieved (huzzah)

↑ yet another attempt to stick to human image

edit: I lied, his thumbs are slightly shorter than middle fingers (alas)

While as I said the bottom phalange of thumb is a part of our palm, DCA still has the "original" shape of palm and the giant external thumb (this one actually makes sense, because it would be inconvenient if he had a concave)

He has smaller palm than we do.

the top tips of what would be metacarpal bones (the lowest long bones) are given for hinges. That makes the palm smaller.

Plus, with how his thumbs are generally bigger and his other fingers are made longer at tips (and pinkies made longer in everything), that makes his palm smaller too.

Also the bottom joint of our proximal phalanges (the base of fingers) is a part of our palm if you look at from inner side but attendant has them separately from palm (for obvious reasons - he wouldn't be able to move them under the casing)

I mentioned (on the picture) how the positions of fingers are a bit jambled for the attendant. Let me clarify more: the most inaccurate finger would be index one (since it's on the peak of the "ladder") and the most accurate are middle (except the tip needs to be a tiny bit longer but I've reached the border of my canvas), thumb and probably pinkie.

so the position of index finger is off but in otherwise the proportion more or less works for the attendant.

Yes, I might had edited it so it would be more ideal but I thought about it too late, plus my main focus was on the opposed finger problem

The conclusion? Yeah, they have solved the problem with hand movement. Given that the hinges, I assume, rotate at all angles, attendants have more than fine motor skills.