Sunday, February 28, 2010

Why Didn't I Think of That?

It's not often that I see something in the news or online that I want to smack my forehead and regret not thinking of it. This is one of those cases: moon exploration via telepresence. The basic idea is to send a slew of humanoid robots to the moon, each equipped with a variety of sensors and actuators to roughly correspond to human operators down on Earth.

The trouble is, the article doesn't give due weight to the three-second delay. Three seconds is huge, as anyone who played first-person shooters online in the 90s knows. Lag is a major factor in error, and three seconds takes a human operator well out of the range of reacting naturally to events. In the paper linked, they only go as far as 225 ms lag time, an order of magnitude faster than is being talked about here. I have no doubt that some operators will become very skilled at this delay (though I really wouldn't want to share a road with them driving home after a long session!) but the learning curve will be awfully steep, and potentially expensive.

Part of the solution to that problem will be extensive simulation. Simulators can be built right now that would get the broad strokes right in terms of gravity. The lunar regolith composition will be tough to get the feel right, but hey, they have access to people who've been there and can offer pointers.

To me, though, the answer is to scratch the humanoid part of the telepresence plan. The more the operator expects the robot to act like a human, the more frustrating the experience will be. Locomotion would be the first target -- even in the low gravity, it would be far too easy to trip and fall. Walking would quickly become a chore anyway. A wheeled or treaded robot would be my first choice, but would not be terribly mobile, and those mountains would be awful temptations. I would go for a centaur-like robot, maybe built on a Big Dog chassis: an internal controller would take care of staying upright. The feet would have to be modified, but that's do-able.

The user-controlled manipulators could sit on top of that, taking care to keep the center of gravity low. I would personally prefer (at least for the first few attempts) a modal system where the operator can either move the robot or move the manipulators, not both at once. Part of this is so that the operator's time isn't divided, but also to allow centering and balancing routines to ensure that the robot doesn't fall over.

As for getting a bunch of robots to the moon in the first place? If only there were a commercial competition devoted to getting robots onto the surface of the moon cheaply...

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