CMU taught a robot dog to walk on a balance beam

While discussing humanoid robots not long ago, someone told me that their main problem with the form factor is that – from an evolutionary perspective – we’re not particularly well built. That’s not to say our bodies haven’t served us well, of course.

They’ve been doing the trick for a few hundred thousand years. It’s more that if you sit down with a talented product designer and ask them to create something from scratch, some concern will likely lead them in an entirely different direction.

Balance is on this list. Again, we did just fine, all things considered, but if balancing was high on your list of priorities, you might opt ​​for something with four legs and a lower center of gravity.

This ready-to-use dog robot is a great starting point. The quadruped is very stable in its standard locomotion. As you’d probably expect, that changes quickly when you, for example, stick it to the top of a balance beam. That’s the kind of challenge you live for, though, if you’re part of a lab like Carnegie Mellon University’s Robotics Institute.

“This experience was huge,” says Assistant Professor Zachary Manchester. “I don’t think anyone has ever successfully walked on a balance beam with a robot before.”

As to why that’s such a big challenge… for starters, these robots aren’t designed to do that. Again, if you’re that omnipotent designer, you’ll add more flexibility and balance, to begin with. The solution the team landed on is this big backpack you see in the photo above. It’s a reaction wheel actuator (RWA) – something used to help control the altitude of satellites.

“You basically have a big flywheel with an engine attached,” adds Manchester. “If you spin the heavy flywheel one way, it spins the satellite the other way. Now take that and put it on the body of a quadruped robot.

CMU Notes:

Manchester said it was easy to modify an existing control framework to account for RWAs, as the hardware does not change the mass distribution of the robot, nor does it have the common limitations of a tail or a spine. Without having to consider these constraints, the hardware can be modeled as a gyrostat (an idealized model of a spacecraft) and integrated into a standard model-predictive control algorithm.

Why, you might ask, would anyone spend the time developing such a thing? Besides the obvious satisfaction of watching a robot dog walk on a balance beam, the most immediate response is search and rescue. This has long been a key application for these types of robots – sending machines where you wouldn’t normally send humans. It’s pretty easy to see why balance is super important in such a scenario.