Disney Research have designed the first-ever one-legged hopping robot that runs entirely on lithium batteries. The happy robot is able to stabilize by using its only leg thanks to a ‘linear elastic actuator in parrallel’ — or LEAP — comprised of a voice coil actuator in parallel along with two compression springs. Two servo motors then make sure the robot jumps up and down.
By concentrating on building a light, efficient robot, Joohyung Kim, associate research scientist at the Disney Research and his colleagues, Katsu Yamane and Zachary Batts, developed a robot weighing a little less than 5 pounds and about one foot in height. Most one-legged hopping robots are designed with hydraulic devices, but this technique requires off-board motors and it is energetic enough to pose issues outside of a controlled laboratory, Yamane said.
The robot is built around a central voice coil actuator (yep, the same thing that moves in and out in speakers), and a pair of the springs to give it extra bounce. A flat platform on the top of this houses the batteries, controlling computer, and sensors, and the whole thing is balanced by an algorithm which was trained in 3D simulations. The result is a robot that can hop about the untethered for up to 19 jumps before falling over.
This leg is connected to a torso which contains battery power, sensors and other electronics. To keep the upper torso level during hopping, the angle of the leg is adjusted at each hop using 2 standard servo motors. The torso is only about twice as heavy as the leg, whereas most of hoppers have torsos that are much heavier in relation to the leg, which helps them achieve dynamic balance.