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## Quadrocopters Throwing and Catching an Inverted Pendulum103

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.'"

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## Quadrocopters Throwing and Catching an Inverted Pendulum

• #### Re:This is cool and all, but... (Score:5, Informative)

on Friday February 22, 2013 @12:18PM (#42980507)

Because the round bits on the end act as pivots that are below the center of mass.

• #### Re:Why is it called an inverted pendulum? (Score:4, Informative)

on Friday February 22, 2013 @12:30PM (#42980665)
Because an inverted pendulum is a class and a stick is a particular instance (as it would be a drunkard). [wikipedia.org]
• #### Re:Why is it called an inverted pendulum? (Score:5, Informative)

on Friday February 22, 2013 @12:36PM (#42980771)
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.
• #### Re:Fantastic! (Score:2, Informative)

by Anonymous Coward on Friday February 22, 2013 @01:40PM (#42981589)

At one point in the film there is a cloud of ???. Is this the staff being ground up due to an apparent miss?

The end of the staff has a small balloon on it, filled with powder -- see explanation further down the linked page. Sounds like a small hacky-sack with a rubber (grippy) surface. They call this a "damper" and one popped open.

Adding my compliments to the rest -- very cool demonstration of control theory.

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