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Quadrocopters Throwing and Catching an Inverted Pendulum
derGoldstein writes "We've seen some very impressive aerobatics performed by quadrocopters before, but this is getting ridiculous. Robohub points to the latest advancement from the Flying Machine Arena, which developed algorithms that allow quadrocopters to juggle an inverted pendulum. One of the researchers working on it said, 'We started off with some back-of-the-envelope calculations, wondering whether it would even be physically possible to throw and catch a pendulum. This told us that achieving this maneuver would really push the dynamic capabilities of the system. As it turned out, it is probably the most challenging task we've had our quadrocopters do. With significantly less than one second to measure the pendulum flight and get the catching vehicle in place, it's the combination of mathematical models with real-time trajectory generation, optimal control, and learning from previous iterations that allowed us to implement this.'"
It don't mean a thing if they don't compute that swing.
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It is now clearly obvious: in the future, the weapon of choice to fight robots will be an aluminium baseball bat.
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Because the round bits on the end act as pivots that are below the center of mass.
It's about sounding "science", as much as it a well defined scientific concept. An inverted pendulum is a well defined controls problem, where you take an unstable system and make it stable with your control laws. This is often solved in one dimension as part of undergraduate controls classwork with a cart and a stick balanced above it. The description of throwing and catching inverted pendulums perfectly describes what they are doing.
On the other hand, if they said they were throwing and catching a stick, I'd assume they were simply catching it. The balancing the unstable system with their control laws would not be assumed. Hope this helps.
This looks like it was achieved using motion capture equipment, as seen by the usage of retro-reflective balls (see them shine at 1:44). If that's the case, it would imply that the computing was done remotely. Motion capture gear typically works at 120 frames per second, which would give the system enough time resolution to figure this out on the fly with a decent PC on the back-end.
It'll be a while before the quadrucopters can do this in their own but the program figuring out the catching move is impressive nonetheless.
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