Robot runner concept art

Ultra-athletic, jumping robots could be designed with help of mathematical model

Image credit: Dreamstime

US researchers have investigated why robots struggle to jump, unlike many small animals, and suggested how powerful bouncing, snapping and tossing could be added to their skillsets.

Many very lightweight and small animals, such as fleas, can jump enormous heights and distances compared to their body size, as well as delivering surprisingly powerful bites, snaps and blows. For instance, the mantis shrimp delivers 69mph (111km/h) blows with his hammer-like mouthparts to break open unfortunate victims’ shells. Meanwhile, a trap-jaw ant can snap its mouthparts at more than 140mph (225km/h) and the tiny hydra fires poisonous spears which accelerate 100 times faster than a bullet.

Now, researchers based at Duke University, North Carolina, have suggested a mathematical model to explain how these tiny animals produce such powerful movements. This model could also be used to suggest how biomimetic robots - robots inspired by biology - could be built which could compete with the power and speed of these creatures.

These creatures are known to be capable of these incredible feats thanks to spring-loaded body parts which can be cocked and released, much like a crossbow; bulky muscles have little to do with these abilities. However, little was known about how these elastic body parts worked together to provide this power. Traditional mathematical models fail to take into consideration the inevitable trade-off between force and speed in spring-like and latch-like biological mechanisms.

The biologists have created a mathematical model of rapid motion on small scales which takes into account this trade-off, and which can be applied in various situations.

“Part of our goal was to try to develop a model that is equally generalizable to biological or engineered systems,” said Professor Manny Azizi, an ecologist at the University of California-Irvine who specialises in the jumping motion of frogs.

The researchers used data on the powerful movements of 104 species of plants and animals, and compared this data to similar movements of small biomimetic robots inspired by ultrafast biological movement, and accounting for trade-off between speed and power in both biology and engineering in their resultant model. This model takes a set of mechanisms and produces details of the theoretical top speeds, accelerations and other performance metrics at different masses.

According to the model, robots may be unable to outjump small insects due to the necessity for these insects’ intricate biological components to be perfectly fine-tuned to each other over millions of years of natural selection. The model could be used, the researchers suggest, helping roboticists design the sets of mechanisms necessary to enable ultrafast and ultra-powerful robots.

“If you have a particular size robot that you want to design, for example, it would allow you to better explore what kind of spring you want, what kind of motor you want, what kind of latch you need to get the best performance at that size scale, and understand the consequences of those design choices,” said Professor Sarah Bergbreiter, a University of Maryland mechanical engineer who designs tiny, jumping robots.

The model could also be used to identify the range of appropriate weights for a robot which is required to be capable of certain super-movements.

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