A mechanical jumper developed by UC Santa Barbara engineering professor Elliot Hawkes and his collaborators is capable of reaching the highest height – about 30 meters – of any jumper to date, which he either engineered or organic. This feat represents a new approach to the design of jumping devices and advances the understanding of jumping as a form of locomotion.
“The motivation came from a scientific question,” said Hawkes, who as a roboticist seeks to understand the many possible methods for a machine to navigate its environment. “We wanted to understand what the limits of technical riders were.” Although there are centuries of studies on biological jumpers (i.e. us in the animal kingdom) and decades of research on mostly bio-inspired mechanical jumpers, he said, two lines of research have been somewhat separated.
“There really hadn’t been a study that compares and contrasts the two and how their limits are different — whether technical jumpers are really limited to the same laws as biological jumpers,” Hawkes said.
Their research is published in the journal Nature.
Big spring, small motor
Biological systems have long served as the first and best models of locomotion, and this has been especially true for jumping, defined by researchers as “motion created by the forces applied to the ground by the jumper, while maintaining a constant mass” . Many engineering riders have focused on duplicating the designs provided by evolution, and with great effect.
But the elements that create a jump in a biological system can be limiting for engineered systems, said Charles Xaio, who holds a Ph.D. candidate in Hawkes’ lab.
“Biological systems can only jump with as much energy as they can produce in a single muscle stroke,” Xaio said. Thus, the system is limited in the amount of energy it can give to push the body off the ground, and the jumper can only jump so high.
What if there was a way to increase the amount of energy available? For technical jumpers, there are: they are able to use motors that click or spin to take many hits, multiplying the amount of energy they can store in their spring. The researchers called this ability “labor multiplication,” which is found in technical sweaters of all shapes and sizes.
“This difference between energy production in biological and technical jumpers means the two would have to have very different designs to maximize jump height,” Xiao said. Animals must have a small spring – just enough to store the relatively small amount of energy produced by their muscle movement alone – and a large muscle mass. On the other hand, technical jumpers should have as big a spring as possible and a small motor.”
The researchers took this knowledge and designed a jumper quite different from biological jumpers: the size of its spring relative to its motor is almost 100 times greater than that found in animals. In addition, they designed a new spring, seeking to maximize its energy storage per unit mass. In their tension-compression hybrid spring, carbon fiber compression arcs are crushed while rubber bands are stretched by the pull of a line wrapped around a motorized axis. The team found that binding the edges of the arches outward in the middle with tension rubber also improved the strength of the spring.
“Surprisingly, the rubber makes the compression spring stronger,” Hawkes said. “You can compress the spring more without it breaking.”
The jumper is also designed to be lightweight, with a minimalist locking mechanism to release the energy needed for jumping, and aerodynamic, with folded legs to minimize air drag during flight. In total, these design features allow it to accelerate from 0 to 60 mph in 9 meters per second – an acceleration force of 315 g – and reach the height of about 100 feet in the researchers’ demonstrations. For powered jumpers, that’s “close to the achievable limit of jump height with currently available materials,” according to the study.
This design and the ability to overcome the limits set by biological designs paves the way for the reinvention of jumping as an efficient form of mechanical locomotion: jumping robots could reach places where only flying robots currently reach.
The benefits would also be more pronounced off Earth: hopping robots can travel efficiently across the moon or planets, without facing obstacles on the surface, while gaining access to features and perspectives inaccessible to earth-based robots. field.
“We calculated that the device should be able to jump 125 meters in height while jumping half a kilometer forward onto the moon,” Hawkes said, pointing out that gravity is 1/6 that on Earth and that there is virtually no air drag. . “That would be a giant leap for technical jumpers.”