Robot feet

Do robots need feet, and by extension legs? Are there actually many applications where feet would perform better than wheels or tracks?

What kind of feet should they have? Is simplicity better?

How many legs? Two legs bad, four legs good?

What kind of problems need to be solved to have heavy machinery walking about the place?

Legs are more useful than wheels on uneven or very steep terrain, like stairs. Two legs are often quite unstable and three would have a strange walking pattern, so four is probably good. The kind of feet robots should have would depend on their job, in a similar way to us having different shoes for different situations.

Isaac Asimov brought it up in one of his robot stories. (I don't remember which one.) The idea was that the first robots were designed as centaurs, but they were kind of offputting to people, and they had problems getting around small corners occasionally, so more effort was put into making the robots bipedal.

They're actually finding that six legged robots are better at terrain changes and speed than two or four legs.

edited 8th Feb '13 8:51:09 PM by DrunkGirlfriend

It seems to me that these robots have legs, but no feet.

The more legs you have, the less necessary feet become. It's a question of balance. hexapods usually walk in a way that leaves three legs on the ground at all times, like a tripod, so they're stable as-is. Bipeds, on the other hand, need large feet in order to make the fine adjustments necessary to balance.

edited 9th Feb '13 3:38:46 AM by Elfive

Thats one of the things I was thinking about, less legs equal bigger feet.

Human feet, for all their usefulness aren't the best design for bipedal robots, something flater is probably better.

They also have the benefit that they would need far less processing power to control their legs, compare insects to mammals with four legs, extra legs means you can make more errors when moving without consequences.

edited 9th Feb '13 3:48:31 AM by MCE

Well, the most advanced bipedal robot I can think of right now is ASIMO, and he has fairly small feet, but I think he uses a hell of a lot of CPU just to stay upright.

edited 9th Feb '13 4:02:12 AM by Elfive

Freely swinging bipedal robot legs are a lot more stable and don't need much processing power.

Clearly we should just find a way to make all robots hover, that should make legs redundant.

<—- Like this one? Wait...

Interesting. In a story, I had aliens with ungiligrade legs, who walked on the tips of their toes. Though they're humanoid, I was under the impression that human legs and feet were generally inefficient for fast movement and had been looking at what I thought to be a more efficient model. Standing on my toes or the balls of my feet, I've found, makes no difference to my balance (though you can't keep it up, of course; humans weren't built for motion of that kind), and sprinters, IIRC, hit the ground toes-first.

I had realized that a biped ungiligrade might be problematic given weight, balance, etc., but thought it could be solved by giving them tails and enlarging and strengthening the ankles, sort of like a horse's—that way the weight wouldn't be resting so much on the feet.

I also considered giving them fleshy "hooves", but I realized that feet with completely flat soles wouldn't work for a two-legged creature as they'd be unable to roll their feet and generate forward momentum.

Maybe I should rethink this.

Then again, we're discussing robots, which currently lack the fine motor skills of humans.

Also, maybe relevant to this conversation: The humanoid-vs.-nonhumanoid question becomes a plot point in the novel Robopocalypse, when a humanoid robot in Afghanistan goes homicidal and starts killing American soldiers. In the words of the POV character, "Humanoids are bad for combat." The robot headshots his entire squad and he takes it out by shooting out its knee joints. Throughout the novel, the robots designed for combat are very much nonhuman—flying drones, turrets with wheels, etc.

edited 11th Feb '13 4:37:45 PM by Alma

A bipedal robot would not be best for combat though. Regardless of how big the feet are you still end up with a triangular point where the robot will tumble over.

The humanoid robot wasn't ever intended for combat. It was sort of an American ambassador to the Afghans. It only went homicidal after an uplink with an AI who wanted to Kill All Humans. The point was that it was precisely because of its humanoid design that it was easily defeated, though it was still quite deadly in the interim.

A robot with points for feet would be good at running, but would probably fall over the minute it stopped.

Unless it could embed them in the floor or something.

Gyroscopes might help.