Taking a Leap in Bioinspired Robotics

Estimated reading time: 7 minutes

In 2009, Kim accepted an assistant professorship in MIT’s Department of Mechanical Engineering, where he established his Biomimetic Robotics Lab and set a specific research goal: to design and build a four-legged, cheetah-inspired robot.

“We chose the cheetah because it was the fastest of all land animals, so we learned its features the best, but there are many animals with similarities [to cheetahs],” Kim says. “There are some subtle differences, but probably not ones that you can learn the design principles from.”

In fact, Kim quickly learned that in some cases, it may not be the best option to recreate certain animal behaviors in a robot.

“A good example in our case is the galloping gait,” Kim says. “It’s beautiful, and in a galloping horse, you hear a da-da-rump, da-da-rump. We were obsessed to recreate that. But it turns out galloping has very few advantages in the robotics world.”

Animals prefer specific gaits at a given speed due to a complex interaction of muscles, tendons, and bones. However, Kim found that the cheetah robot, powered with electric motors, exhibited very different kinetics from its animal counterpart. For example, with high-power motors, the robot was able to trot at a steady clip of 14 miles per hour — much faster than animals can trot in nature.

“We have to understand what is the governing principle that we need, and ask: Is that a constraint in biological systems, or can we realize it in an engineering domain?” Kim says. “There’s a complex process to find out useful principles overarching the differences between animals and machines. Sometimes obsessing over animal features and characteristics can hinder your progress in robotics.”

A “secret recipe”

In addition to building bots in the lab, Kim teaches several classes at MIT, including 2.007, which he has co-taught for the past five years.

“It’s still my favorite class, where students really get out of this homework-exam mode, and they have this opportunity to throw themselves into the mud and create their own projects,” Kim says. “Students today grew up in the maker movement and with 3-D printing and Legos, and they’ve been waiting for something like 2.007.”

Kim also teaches a class he created in 2013 called Bioinspired Robotics, in which 40 students team up in groups of four to design and build a robot inspired by biomechanics and animal motions. This past year, students showcased their designs in Lobby 7, including a throwing machine, a trajectory-optimizing kicking machine, and a kangaroo machine that hopped on a treadmill.

Outside of the lab and the classroom, Kim is studying another human motion: the tennis swing, which he has sought to perfect for the past 10 years.

“In a lot of human motion, there’s some secret recipe, because muscles have very special properties, and if you don’t know them well, you can perform really poorly and injure yourself,” Kim says. “It’s all based on muscle function, and I’m still figuring out things in that world, and also in the robotics world.”

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