Locomotion, the ability to move from one place to another, is an essential survival strategy for virtually every organism. Adapting to the unpredictable terrain they run into, cells, fungi and microorganisms autonomously move and change shape to explore their environments, while animals run, crawl, slither, roll and jump.
But despite advances in computing power and AI, human-made robots still struggle to imitate this movement, especially in new and unpredictable terrain.
In a paper published March 12 in Nature, physicists from the University of Amsterdam and the University of Chicago showcase a series of ‘odd’ objects that are remarkably good at moving across any terrain they encounter—including uphill and over obstacles placed in their way. But unlike traditionally designed robots, these have no centralized control or brain; they are simply responding to small forces on each other and the terrain.
This offers a new way to accomplish locomotion, the scientists said, and could solve problems in robot movement.
“The striking thing about this is its minimalism,” said Colin Scheibner (PhD’23), co-first author on the paper. “There’s not a complicated algorithm powering its decisions. I feel there’s something powerful about its simplicity, which approaches the question of movement in a different way.”
Brainless motion from odd elasticity
Instead of a traditional robot design, the ‘odd’ robots are instead a set of simple motorized devices, connected by elastic springs. When turned on, the motions of the building blocks interacting with each other propels the whole set forward together.
The key difference is that these objects aren’t being steered or controlled by a centralized “brain,” which sets them apart from most previous attempts at robotic movement. Instead, the motion comes solely from the interactions between the objects’ motorised building blocks.
“The building blocks exert forces that are nonsymmetric and nonreciprocal. This means that a building block A reacts to its neighbouring building block B differently than how B reacts to A,” explained Jonas Veenstra, co-first author of the publication and a PhD student at the University of Amsterdam.
As the object moves, a self-reinforcing cycle is created. The terrain deforms the object, the object’s building blocks sense and respond by deforming the object further—and the object moves forward and encounters new terrain.