An algorithm describes the movement by change of body shape

2023-08-10 13:21:59

The jellyfish is one of the animals that moves by changing its body appearance – CALTECH

MADRID, 10 Ago. (EUROPA PRESS) –

A single algorithm is capable of describing the movement of animals based on the contortion or shape change of their bodies, Caltech researchers have discovered.

This type of locomotion is found in snakes when they glide, in manta rays when they swim and even in cats when they twist to land on their feet as they fall.

The contortions of a falling cat and a sideways snake may not seem like they have much in common, but the new algorithm describes both types of movement and the movements of many other animals that move simply by changing shape.

An article describing his work appears in the August issue of ACM Transactions on Graphics.

“You have all kinds of creatures that have in common that they move by changing their shape,” he says. it’s a statement Schröder, the Shaler Arthur Hanisch Professor of Computer Science and Applied and Computational Mathematics. “A classic example is a single-celled organism. How does it move? It doesn’t have legs. It doesn’t have wings to fly. The only thing it can really do is change its shape.

“Once you understand that basic observation, you see that there are all sorts of creatures that move by changing their shape. A snake makes an undulating motion and yet manages to move forward. Astronauts can spin in zero gravity by making a move of dance that manages to rotate them without needing to push a surface”.

Schröder says that all of these types of motion can be explained by the principle of least dissipation, a concept that postulates that natural systems will always try to be as efficient as possible. As an example, he cites an ice skate, which can easily slide forwards or backwards on ice, but has great difficulty sliding from side to side. If a person wears ice skates and wants to skate forward, he pushes his skates to the sides, away from the center line of his body. Since it’s hard for a skate to skate sideways, the skates (and the person wearing them) will move forward, since forward motion is easier and more efficient. The system consisting of the skater, the skates and the ice favors forward movement because it wastes less energy.

The same principle is at work when a snake undulates its way across the sandy soil of a desert.. A snake, being long and thin, can slide back and forth much more easily than it can slide sideways. Since that undulation causes your body to slide sideways in a back and forth motion, a lot of energy would be lost due to friction, unless the snake moves forward while undulating. Since the movement along the snake encounters less friction, the system favors it, and the snake glides along its merry, scaly path.

All of these types of locomotion were modeled on computers using the principle of least dissipation as a starting point. The animals were represented as sets of flexible nodes connected by rigid bars and allowed the researchers to examine how creatures move in a simulated space and compare it to real life data.

Guided by the principle of least dissipation (and other mathematics), these animal models displayed movement remarkably similar to that seen in their real-world counterparts.

“It’s beautiful that you can identify a fairly simple guiding principle from a whole class of different types of movement.“, says Schröder. “It is not 100 percent accurate, but it shows a remarkable agreement with the movement observed in real life, which suggests that it captures an important part of what happens in nature. There is a certain mathematical beauty when you have a very simple principle that can explain a lot of things at once.”