3D-Printed Robot Hand Can Play the Piano

A robotic hand fabricated using multi-material 3D printing is exploring new possibilities for passive movements using mechanics, according to researchers at Cambridge University.

Researchers have developed a 3D-printed robotic hand that shows innovation in mechanical design by playing the piano just by moving its wrist.

A team from Cambridge University developed the robot, which they admit is no musical virtuoso—and also not the first of its kind. However, what’s unique about the invention is that it can play simple musical phrases on a piano with a limited range of motion thanks to a simple design that used multi-materials 3D-printing, they said in a news release.

piano robot
Scientists have developed a 3D-printed robotic hand that can play simple musical phrases on the piano by just moving its wrist. (Image source: Josie Hughes, Cambridge University)

Replicate Bones and Ligaments

Researchers fabricated the robot by 3D-printing a combination of soft and rigid materials to replicate all of the bones and ligaments—but not muscles or tendons—in a human hand.  While this design limited the robot’s range of motion as compared to an actual hand, it still was able to achieve a wide range of movement thanks to the mechanical design, said Josie Hughes from Cambridge’s Department of Engineering.

“Smart mechanical design enables us to achieve the maximum range of movement with minimal control costs,” she said. “We wanted to see just how much movement we could get with mechanics alone.”

The answer is: quite a lot, researchers found. Using what’s called “passive movement”—i.e., the robot’s fingers can’t move independently—it could mimic different styles of piano playing without changing the material or mechanical properties of the hand. Researchers said the results of their study—an article about which they published in the journal Science Robotics—could help inform the design of robots that are capable of more natural movement with minimal energy use.

“We can use passivity to achieve a wide range of movement in robots: walking, swimming, or flying, for example,” Hughes explained. “Smart mechanical design enables us to achieve the maximum range of movement with minimal control costs. We wanted to see just how much movement we could get with mechanics alone.”

The Key is the Printing

3D printing is key to the team’s achievement, researchers said. It allowed them to integrate soft components into more complex robotic ones, so the robotic hand also is soft, like skin on a human hand. However, it has intelligence in its mechanical system rather than using a common command center—akin to the human brain—to achieve movements, researchers said.

“Our bodies consist of smart mechanical designs such as bones, ligaments, and skins that help us behave intelligently even without active brain-led control,” explained Fumiya Iida, who led the research team. “By using the state-of-the-art 3D-printing technology to print human-like soft hands, we are now able to explore the importance of physical designs, in isolation from active control, which is impossible to do with human piano players as the brain cannot be ‘switched off’ like our robot.”

Researchers “taught” the robot to play by considering how the mechanics, material properties, environment, and wrist actuation all affect the dynamic model of the hand, they said. By actuating the wrist, they could choose how the hand interacts with the piano. This allowed the embodied intelligence of the hand to determine how it interacts with the environment. 

Just the Basics, For Now

The researchers programmed the robot to play a number of short musical phrases with both staccato and smooth, or legato, notes only by using the movement of the wrist, Hughes said. “It’s just the basics at this point, but even with this single movement, we can still get quite complex and nuanced behavior,” she said.

Despite the limitations of the robot hand, the researchers say their work will influence and potentially lead to further research into the underlying principles of skeletal dynamics to achieve complex movement tasks. They also believe it can inform scientists as they explore where the limitations for passive-movement systems lie, Iida said.

“This approach to mechanical design can change how we build robotics,” he said. “The fabrication approach allows us to design mechanically intelligent structures in a way that is highly scalable.”

Elizabeth Montalbano is a freelance writer who has written about technology and culture for 20 years. She has lived and worked as a professional journalist in Phoenix, San Francisco and New York City. In her free time she enjoys surfing, traveling, music, yoga and cooking. She currently resides in a village on the southwest coast of Portugal.

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