Why Is It so Hard to Build a Robot More Athletic Than a Frog?

A new mathematical model could help explain why robots can’t compete with small-but-mighty performers in the animal kingdom—for now.

Certain animals, like frogs, exhibit physical abilities far beyond what can be reproduced in robots of a similar size. (Image courtesy of Nicolas Reusens, Barcroft.)

Certain animals, like frogs, exhibit physical abilities far beyond what can be reproduced in robots of a similar size. (Image courtesy of Nicolas Reusens, Barcroft.)

When it comes to athletic performance, robots still lag behind some of the star athletes in the natural world. Certain tiny organisms, like high-jumping frogs and hard-chomping insects, boast incredible combinations of speed and power that are the envy of microrobot designers everywhere. Engineers have been trying and failing to reproduce the physical characteristics of these animals in their robots for years. A new study recently published in Science is helping to explain why.

Modeling Nature

The study was conducted by researchers from seven different universities over a number of years. The team set out to develop a mathematical model that could explain the explosiveness of certain movements observed in nature—and help robots to close the gap. The team focused on a few extreme examples of this small-scale power, such as the trap jaw ant’s 140-mile-per-hour mandibles.

The secret to the power of these animals’ movements is in their unique, spring-loaded anatomical characteristics. Sheila Patek, a research team member from Duke University, likened these systems to an archer’s bow. For that reason, the team’s model accounts for the fundamental tradeoffs observed in any moving component, be it mechanical or organic. Springs and latches, or their biological equivalents, have certain constraints based on a wide range of variables. The model will allow users to input parameters based on the stiffness, mass and composition of these components and then get back an estimate of the maximum physical performance the entire system might produce.

Robots Versus Animals: Coming Soon?

For engineers looking to build super-powered microrobots, the model could provide invaluable design guidance going forward. The physical tradeoffs that the model is able to account for should help designers isolate limiting variables in a kinetic system. “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 Sarah Bergbreiter, a researcher from the University of Maryland. In other words, if a given component is limiting the kinematics of a system, the model can guide engineers toward an alternative solution.

The challenges associated with developing a machine that can match the sort of athletic performance observed in some of nature’s top performers remain daunting. The research team ultimately concluded that the biggest factor differentiating animals from robots today isn’t material strength—it’s the connectedness of a full motor function. Such powerful and rapid movements seen in nature require extremely intricate and integrated synchronization. In frogs, fleas and fly traps, that harmony occurs naturally. Scientists will no doubt use this model going forward to bring microrobots closer to such calibration.

To learn about a cool way that nature is already inspiring advances in robot design, check out Six-Legged Robot Improves on Nature’s Design.