Cubli, balancing cube, Institute for Dynamic Systems and Control, ETH Zurich, Zurich, Switzerland

The Cubli is a 15 x 15 x 15 cm cube that can jump up and balance on its corner. Reaction wheels mounted on three faces of the cube rotate at high angular velocities and then brake suddenly, causing the Cubli to jump up. Once the Cubli has almost reached the corner stand up position, controlled motor torques are applied to make it balance on its corner. In addition to balancing, the motor torques can also be used to achieve a controlled fall such that the Cubli can be commanded to fall in any arbitrary direction. Combining these three abilities -- jumping up, balancing, and controlled falling -- the Cubli is able to 'walk'.

Lead Researchers: Gajamohan Mohanarajah and Raffaello D'Andrea

This work was done at the Institute for Dynamic Systems and Control, ETH Zurich, Switzerland and was funded in part by the Swiss National Science Foundation (SNSF), grant number 146717.

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Gajamohan Mohanarajah (ETH Zurich, Lab of Raffaello D'Andrea) at ZURICH.MINDS 2013: The Cubli. A cube that can jump and balance. Event curated by Rolf Dobelli

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Watching a cube jump suddenly onto a corner and balance there indefinitely is jarring at first. Cubli can do just that! Doc North investigates Raffaello D'Andrea's lab at the Institute for Dynamic Systems and Control at ETH Zurich, Switzerland where this robotic advance was developed, and ponders the implications.

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This video presents the One-Wheel Cubli, a three-dimensional pendulum system, that can balance on its pivot using a single reaction wheel. How is it possible to stabilize the two tilt angles of the system with only a single reaction wheel?

The key is to design the system such that the inertia in one direction is higher than in the other direction by attaching two masses far away from the center. As a consequence, the system moves faster in the direction with the lower inertia and slower in the direction with the higher inertia. The controller can leverage this property and stabilize both directions simultaneously.

Researchers: Matthias Hofer, Michael Muehlebach, Raffaello D'Andrea
Design: Michael Egli, Matthias Müller
Voice: Helen Hanimann

This work was carried out at the Institute for Dynamic Systems and Control, ETH Zurich, Switzerland.

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