On Friday, we posted a video of Sangbae Kim (from the MIT Biomimetic Lab) getting drenched in the name of ALS. The robot doing the drenching was MIT's Cheetah, but it was much, much different than than the version of Cheetah that we were familiar with from last year, and we speculated that the new version might be out running untethered.
We were wrong: it's not running untethered, it's bounding untethered. And unconstrained. And outdoors!
Two things strike us as particularly amazing about this: the first thing is that it's quiet, powered by electric motors and batteries. We've come to expect that compact systems capable of delivering high amounts of power rely on liquid fuels and hydraulics, because that's how you get the most power density: it's why Boston Dynamics uses gasoline engines to power hydraulic pumps on all of its dynamic robots. Also, high torque electric motors (like you'd need to get a robot to jump) have a tendency to overheat and destroy themselves, but MIT seems to have solved all of these issues, since they have a bounding, battery-powered robot that works. We're not sure yet how long it works for, but it works.
The second thing that's amazing about MIT's Cheetah is that it does not seem to disintegrate into a pile of splinters on landing after jumping as high as it does. Cheetah (Cheetah 2, technically) weighs 31 kilograms and is 0.7 meter long: as you can see in the video, it's not small, and it's not lightweight. It's also moving fast and jumping high, clearing 33 centimeter obstacles at 10 mph, with the potential to hit 30 mph. We don't know all the details (yet, we're working on it), but based on what we know about earlier versions of Cheetah, we're imagining that a lot of careful thought has been put into the bioinspired design of the legs and spine of the robot, along with some very powerful custom motors.
"Bounding," which is what Cheetah is doing here, is a gait that's somewhere in between a canter, which is more dynamic than a trot, and a gallop, which is the most dynamic stable gait. Bounding might not be a typical gait for real cheetahs; it's more like what you might see in a lazy rabbit. But getting from bounding to galloping is not that hard: you just split the legs up, and you're there. Since MIT's Cheetah is based on force control (careful control of the specific amount of force exerted into the ground by the legs and feet), it's gait is flexible and easily adjustable, and robust to minor variations in terrain like you might find out in a grassy field.
MIT was sneaky, and put out this press release before the research was officially presented at IROS (tomorrow), so we'll see what more we can find out when we get a chance to speak to the researchers directly, and update this post when we can.
"Quadruped Bounding Control With Variable Duty Cycle via Vertical Impulse Scaling," by Hae-Won Park, Meng Yee (Michael) Chuah, and Sangbae Kim from MIT, will be presented on Tuesday at IROS 2014 in Chicago.