Marc Raibert: evaluation

Transcript context

…What does the actuation look like? The simple story is that there’s three things going on. There’s something making it bounce. And we had a system that was estimating how high the robot was off the ground and using that. There’s energy that can be in three places in a pogo stick: one is in the spring, one is in the altitude, and the other is in the velocity. And so when at the top of the hop, it’s all in the height, so you could just measure how high you’re going, and thereby have an idea of a lot about the cycle, and you could decide whether to put more energy in or less. That’s one element. Then there’s a part that you decide where to put the foot. And if you think when you’re landing on the ground with respect to the center of mass. So if you think of a pole vaulter, the key thing the pole vaulter has to do is get its body to the right place when the pole gets stuck. If they’re too far forward, they kind of get thrown backwards. If they’re too far back, they go over. And what they need to do is get it so that they go mostly up to get over the thing. And high jumpers is the same kind of thing. So there’s a calculation about where to put the foot, and we did something relatively simple. And then there’s a third part to keep the body at an attitude that’s upright, because if it gets too far, you could hop and just keep rotating around. But if it gets too far, then you run out of motion of the joints at the hips. So you have to do that. And we did that by applying a torque between the legs and the body. Every time the foot’s on the ground. You only can do it while the foot’s on the ground in the air. The physics don’t work out. How far does it have to tilt before it’s too late to be able to balance itself or it’s impossible to balance itself, correct itself?…

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