On that note, we've recently stumbled across Cubli, a little cube-shaped robot made by Gajan Mohanarajah, Ph.D. candidate and research assistant at ETH Zurich. Cubli isn't designed to build a wall or translate slime mold. Instead, it's based on a very simple idea: "Can we build a 15-centimeter-sided cube that can jump up, balance on its corner, and walk across our desk using off-the-shelf motors, batteries, and electronic components?"
Balancing is not necessarily difficult to achieve (although it looks amazing); the trickiest part was in getting the cube to jump up from a resting position to a balancing position, since it releases a burst of energy to do so, and needed to be kept stable. The solution was to use momentum wheels, which are the same kind of flywheel used for altitude control in spacecraft.
These momentum wheels were then also used to help the cube balance by using the reaction torques' acceleration and deceleration.
"These torques are what the Cubli's structure 'feels' when the three motors attached to it accelerate or decelerate the wheels," Mohanarajah explained. "In fact, Cubli's controller tries to minimise wheel velocities in addition to keeping the structure upright. This method is more reactive to external disturbances and reduces vibrations and sensor noise."
The resulting robot is able to jump from a resting position to balancing on an edge, then a corner; and it can "walk" by jumping up, balancing on an edge and falling onto another side of the cube, effectively rolling along. It's really cool stuff, and we'd love to have one of our own just to play with.