A 30 centimeters high robot can jump into the air more than a hundred times its own length: 33 meters – more than a ten-storey flat. It is a super jumper, it gets higher than almost all jumpers in nature and much higher than other motorized jumpers, write researchers from the University of California and Disney Research in Nature†
Jumping robots are usually made after jumping animals or insects. But biology mechanics have limitations that motorized jumpers can work around, the researchers said. They made a model of the limitations, and then designed a robot themselves to show how things could be improved. “This is close to the maximum possible,” they write.
The robot is mainly feather. It consists of four flexible carbon fiber ribs, with rubber bands in the middle. A string runs through the center, which is attached at the bottom and at the top – where the motor sits in a point-shaped space – is rolled up, causing the ribs to bend outwards. The robot is wide, once in the air it takes on a spear shape.
Increasing energy storage is the crux of the robot and the big difference with biological jumpers. The rotating motor acts like a winch that winds the string. This means that with relatively little effort, more energy can be stored than a biological jumper could ever do. Muscles have a limited length and can only make one contraction movement.
The material also helps, the combination of carbon fiber ribs and rubber bands. They can all be put under voltage and have a higher energy density than materials in nature. The springy part is also heavier than the motor, in many biological jumpers the ratio is the other way around.
“The surprising thing about this robot is its relatively large size,” writes Sarah Bergbreiter, mechanical engineer at Carnegie Mellon University in a comment in Nature† “The best jumpers in biology are usually limited to a few grams or less. Higher mass jumpers (like humans) use direct muscle power rather than spring actuation. But this robot has a mass of 30 grams, more than ten times heavier than the largest spring-powered organisms.”
The researchers fantasize about the usefulness of their jumper – for observations on the moon, for example, where it would reach a height of 125 meters. But to be useful in practice, you need to be able to control the jump height better, says Bergbreiter. “And although this robot can get itself ready again, it takes no less than two minutes to do so. Other jumping robots are immediately ready for use.”