Very interesting device that I came across online yesterday. This is Cubli
, a mechanical cube that is capable of balancing itself very effectively, and can even "jump up and walk" across surfaces by performing controlled falls.
The Cubli attains it's balance from multiple inertia sensors
within the device, the measurements of which are fused to get a sense of angular velocity
and tilt of itself on a surface. The hull sensors on it measure the angular velocity of the three reaction wheels within the Cubli. These measurements are used by a nonlinear controller to balance it on a corner, while the angular velocity of the reaction wheels are near zero. This allows the Cubli to balance
on the corner even when it is disturbed.
In order to jump up, the reaction wheels spin rapidly to build up angular momentum
, then the wheels suddenly brake--causing the momentum to be transferred to the Cubli's body which causes it to pop up without needing assistance from outside the device. These jumps and balances can be put in sequences to make it seem as if the Cubli can actually walk.
Specific information about the device (including multiple videos with explanations and demonstrations):http://robohub.org/swiss-robots-cubli-a-cube-that-can-jump-up-balance-and-walk-across-your-desk/
General information about angular momentum: http://en.m.wikipedia.org/wiki/Angular_momentum