OK, here is the most important fact I'll probably learn today: Robots should not wear Doc Martins. (At least not robots of current technology.)
Dexter is, as far as we know, the first dynamically balancing biped robot—that is, the first robot that walks like we do.
There are of course biped robots that walk. The Honda Asimo is the best known. But the Asimo doesn't balance dynamically. Its walk is preprogrammed; if you had it walk twice across the same space, it would put its feet down in exactly the same place the second time. And of course the floor has to be hard and flat.
Dynamically balancing—the way we walk—is much harder. It looks fairly smooth when we do it, but it's really a controlled fall. At any given moment you have to think (or at least, your body does) about which direction you're falling, and put your foot down in exactly the right place to push you in the direction you want to go. Practice makes it seem easy to us, but it's a very hard problem to solve. Something as tall as a human becomes irretrievably off balance very rapidly. When a robot is falling, meaning its center of gravity is not centered over the foot (or feet) on the ground, the error grows by e^(t/.5). If a robot gets more than a few centimeters off balance, it's unlikely to recover, because you just can't move the limbs fast enough to compensate.
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The breakthrough, according to Trevor, was to dramatically improve the robot's sense of where its center of gravity was. None of the commercial gyroscopes were good enough, he said, so he built his own. It also helped to make the feet lighter. The original feet, wearing heavy Doc Martins, were replaced by lighter ones outfitted with Vans. (I'm not joking.)
There's a cool video too. Dexter's walk is still kinda' shaky - reminds me of a newborn calf's first attempts at walking.