MIT's Cube Robot Uses Springy Metal Tongues to Jump

Elastic tongues help this robotic cube make lickey split jumps

2 min read

Evan Ackerman is IEEE Spectrum’s robotics editor.

MIT's Cube Robot Uses Springy Metal Tongues to Jump
Elastic tongues help this robotic cube make lickey split jumps.
Image: MIT

It doesn’t seem like the most exciting form factor for a robot would be a cube, but recently, cube robots have been where it’s at. Balancing cubes, jumping hedgehog cubes, even self-assembling cubes: somehow, cubes can do it all. And if you give them springy metal tongues with which they can elastically lick surfaces like MIT did for some reason, they can jump, bounce, and roll.

Seriously. This robot has metal tongues that it uses to jump. Watch:

This looks a little bit like magic, but we’re reasonably certain that it isn’t. Inside of the robot there are two motorized rotors, each connected to one end of four flattened loops of spring steel. Activating the rotors causes the spring steel loops that I’m just going to go ahead and call tongues to get pulled through rectangular openings (mouths) into a round cavity inside the body of the robot, compressing them. As the rotors continue to turn, eventually the compressed tongues get pulled all the way around back to the mouths, at which point they spring out, releasing that elastic energy all at once and causing the robot to jump.


As long as you keep the rotor turning, you can get the robot to keep jumping more or less continuously. Directional control (to the extent of two possible takeoff angles) is possible by using different mouths at different orientations, and driving the rotor either forwards or backwards to take advantage of them.

MIT tested two different designs for the jumping cube: one hard, and one soft, each 7 centimeters on a side with a mass of 200 grams. The jumping performance of both was identical (20 centimeters vertical), but the soft robot was able to bounce along flat surfaces after landing, as much as doubling the distance it was able to travel. The cubes are completely self contained, with integrated controllers, sensors, and rechargeable batteries, offering a substantial amount of mobility in a very small form factor, with a minimum of complexity.

Future work will give the cubes more power (yay!) to get them jumping higher and farther. While the soft cube seemed to perform better than the hard cube, the researchers will also be trying different soft material to see what works best. Ultimately, they’d like to design a closed-loop controller that will enable the robot to jump and bounce autonomously over rough terrain, and adding more sensors could lead to some interesting applications:

With some light-weight payloads, such as miniature cameras, the robot can be used for exploration tasks. Moreover, a wireless sensor network can be automatically deployed and reconfigured for outdoor surveillance by using a group of our jumping robots. 

“A Soft Cube Capable of Controllable Continuous Jumping,” by Shuguang Li, Robert Katzschmann, and Daniela Rus from MIT CSAIL, was presented at IROS 2015 in Hamburg, Germany

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