Péter Fankhauser

Meet Rezero, the dancing ballbot

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Let me introduce to you Rezero. This little fellow was developed by a group of 10 undergraduate students at the Autonomous Systems Laboratory at ETH-Zurich.


Our robot belongs to a family of robots called Ballbots. Instead of wheels, a Ballbot is balancing and moving on one single ball. The main characteristics of such a system is that there's one sole contact point to the ground. This means that the robot is inherently unstable. It's like when I am trying to stand on one foot.


You might ask yourself, what's the usefulness of a robot that's unstable? Now we'll explain that in a second. Let me first explain how Rezero actually keeps his balance. Rezero keeps his balance by constantly measuring his pitch angle with a sensor. He then counteracts and avoids toppling over by turning the motors appropriately. This happens 160 times per second, and if anything fails in this process, Rezero would immediately fall to the ground.


Now to move and to balance, Rezero needs to turn the ball. The ball is driven by three special wheels that allow Rezero to move into any direction and also move around his own axis at the same time. Due to his instability, Rezero is always in motion. Now here's the trick. It's indeed exactly this instability that allows a robot to move very [dynamically]. Let's play a little. You may have wondered what happens if I give the robot a little push. In this mode, he's trying to maintain his position.


For the next demo, I'd like you to introduce to my colleagues Michael, on the computer, and Thomas who's helping me onstage. In the next mode, Rezero is passive, and we can move him around. With almost no force I can control his position and his velocity. I can also make him spin. In the next mode, we can get Rezero to follow a person. He's now keeping a constant distance to Thomas. This works with a laser sensor that's mounted on top of Rezero. With the same method, we can also get him to circle a person. We call this the orbiting mode. All right, thank you, Thomas. (Applause)


Now, what's the use of this technology? For now, it's an experiment, but let me show you some possible future applications. Rezero could be used in exhibitions or parks. With a screen it could inform people or show them around in a fun and entertaining way. In a hospital, this device could be used to carry around medical equipment. Due to the Ballbot system, it has a very small footprint and it's also easy to move around. And of course, who wouldn't like to take a ride on one of these. And these are more practical applications. But there's also a certain beauty within this technology.






Thank you.




Thank you.

Engineering student Péter Fankhauser demonstrates Rezero, a robot that balances on a ball. Designed and built by students, Rezero is the first ballbot made to move quickly and gracefully — and even dance. (Could the Star Wars sphere droid be real? Watch this and judge.)

About the speaker
Péter Fankhauser · Roboticist

Péter Fankhauser is the leader of a team of students working on Rezero, a robot that balances on a single sphere.

Péter Fankhauser is the leader of a team of students working on Rezero, a robot that balances on a single sphere.