This robot’s extra arm gives it whole-body control

This robot has an extra arm growing out of its back, and it’s not just for decoration. It’s an experimental design to show how controlling limbs centrally can transform the functionality of quadrupedal robots. Zipeng FuXuxin Cheng and Deepak Pathak from Carnegie Mellon University built this agile (and distractingly uncanny) beast.

We recommend subscribing to Deepak’s YouTube channel if you’re a robotics nerd

Raspberry Pi powers the whole artificial neural network. The robot runs untethered with all the computing done onboard. And the team managed to get the cost of the build down way below commercial robots, like Boston Dynamics’ Spot. Their low-cost alternative incorporates parts from Unitree Robotics and Trossen Robotics, and costs around $6K.

What’s wrong with four legs?

Most robots are taught to do things using their arms and legs separately. The Carnegie Mellon team reversed this decoupled approach with their own end-to-end concept for whole-body control. It’s this which unlocks extra dynamic behaviours in the robot. The legs can concentrate on keeping the body stable, and moving it around, while the arm performs finer motor functions.

The single Raspberry Pi-powered neural network controls all the joints, offering 12 degrees of freedom for each of the four legs, and six for the special extra arm sprouting from its back. Fine manipulation and movement are coordinated synergistically.

What can it do?

Finding a cup and placing a pen into it, picking up a cup and putting it in a bin, and pressing a button to open an automatic door to enter a building are all within this robot’s wheelhouse. Grabbing a bit of rubbish out of a bush is especially impressive as the robot can tell it needs to bend its front knee in order to get down close enough to the ground, but keep the rest of the legs straight for stabilisation.

We were also warmed by the ability to wipe a whiteboard clean and to follow a human around using AR tag visual tracking. But maybe we’re just lonely.

This work is going to appear in December at #CoRL2022, an annual international conference on robotics and machine learning. Auckland is hosting this year, so the team’s creation will be performing live demos at the venue during New Zealand’s summertime. Hemispheres are weird.

Saved the tricky stuff for last

If advanced robotics floats your boat, deep-dive into the team’s project site. It’s where we found all of the adorable videos you’ve just been poring over. There’s also a tantalising tab at the top promising code will be available “soon.”

whole-body control robot with extra fancy arm
This is what the robot is capable of…
…and this is how they trained it to do it

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it looks amazing. the new era of new technology to reduce human efforts.

Reply to getinshotproapk


The bit where a leafy twig gets stuck first on the front leg, and then on the back leg, made me chuckle :)

Reply to AndrewS


I’m not sure if that ‘dog’ would be more or less creepy if it had a proper head on a flexible neck!

Reply to Phil Olynyk

Ashley Whittaker

More. Definitely more. Smart boy though.

Reply to Ashley Whittaker


Any news on stocks going back to normal? It’s been too long since we were able to get a Raspberry Pi without “hunting” them for months.
The project that reignited the passion for tinkering with technology is now limited to supporting businesses. It’s pretty sad. I hope there’s a way back to how things were.

Reply to Nick


Might I suggest a Centaur configuration? Four legs for mobility, torso having two arms for grasping with two hands, topped by a neck and head for elevating the camera(s)!

Reply to Alan Purdy

Ashley Whittaker

A Centaur is always the answer.

Reply to Ashley Whittaker


I’m now reminded of the spider-baby in Toy Story!

Reply to AndrewS

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