Search And Rescue Robots Could Be Modeled On Ants
May 22, 2013

Fire Ants Help Researchers Work Towards Better Robot Tunneling And Locomotion

[ Watch the Video: Learning Principles of Underground Locomotion From Ants ]

Peter Suciu for — Your Universe Online

While ants can spoil a picnic, and fire ants are despised for their painful bites, the tiny creatures are masters at tunneling, and this expertise could be put to good use. Researchers are now looking at how fire ants manage to tunnel quickly through even fine, loose sand in an effort to aid the design of search-and-rescue robots.

A team from the Georgia Institute of Technology discovered that fire ants can use their antennae as “extra limbs” to build stable tunnels in the loose sand, and can use these antennae to catch themselves when they fall.

The researchers studied the fire ants in a laboratory using video tracking equipment and X-ray computed tomography, and high speed cameras to record the ants´ behavior. The researchers found that this fundamental principle of locomotion could be utilized by robot teams, making it possible for man-made machines to travel quickly and easily through underground tunnels.

The X-ray computed tomography provided the researchers with a way to study the tunnels the ants built in a variety of test chambers, and provided 168 observations. The researchers also utilized video tracking equipment to collect data on ants moving through tunnels made between two clear plates — which were similar to the “ant farms” sold for children — as well as through a maze of glass tubes of differing diameters.

This maze was mounted on an air piston that was periodically fired, dropping the maze with a force of as much as 27 times that of gravity, and this sudden movement was designed to cause about half of the ants in the tubes to lose their footing and begin to fall. That led to one of the study´s most surprising findings; that the creatures used their antennae to help grab onto the tube walls as they fell.

The findings of this research were sponsored by the National Science Foundation´s Physics of Living Systems program, and were published in the Proceedings of the National Academy of Sciences of the United States of America.

“Locomotion emerges from effective interactions of an individual with its environment. Principles of biological terrestrial locomotion have been discovered on unconfined vertical and horizontal substrates. However, a diversity of organisms construct, inhabit, and move within confined spaces. Such animals are faced with locomotor challenges including limited limb range of motion, crowding, and visual sensory deprivation,” the authors wrote in the paper´s abstract.

“Our hypothesis is that the ants are creating their environment in just the right way to allow them to move up and down rapidly with a minimal amount of neural control,” Daniel Goldman, an associate professor in the School of Physics at the Georgia Institute of Technology, and one of the paper´s co-authors said in a statement. “The environment allows the ants to make missteps and not suffer for them. These ants can teach us some remarkably effective tricks for maneuvering in subterranean environments.”

Goldman, along with graduate research assistant Nick Gravish, carried out a series of studies in which groups of fire ants (Solenopsis invicta) were placed into tubes of soil and allowed to dig tunnels for 20 hours. The researchers simulated a range of environmental conditions by varying the size of the soil particles from 50 microns on up to 600 microns, while also alternating the moisture content from one to 20 percent.

These variations in particle size and moisture content did actually produce changes in the amount of tunnels produced and the depth that the ants dug, the diameters of the tunnels remained the same. This also remained comparable to the length of the creatures´ own bodies: about 3.5 millimeters.

“Independent of whether the soil particles were as large as the animals´ heads or whether they were fine powder, or whether the soil was damp or contained very little moisture, the tunnel size was always the same within a tight range,” Goldman added. “The size of the tunnels appears to be a design principle used by the ants, something that they were controlling for.”

Nick Gravish noted that the scaling effect does allow for the ants to better utilize their antennae. Along with their limbs and body this allows the ants to ascend and descend in the tunnels by interaction with the walls. This also could limit the range of any possible missteps.

“In these subterranean environments where their leg motions are certainly hindered, we see that the speeds at which these ants can run are the same,” added Gravish. “The tunnel size seems to have little, if any, effect on locomotion as defined by speed.”

By analyzing ants falling in the glass tubes, the researchers were able to determine that the tube diameter played a key role in whether the animals could prevent their fall. The researchers hope that future studies could help provide a better understanding of how the ants excavate their tunnel networks, which involves moving massive amounts of soil. That soil is the source of the large mounds for which fire ants are known, and of which are commonly found in the American south.

“A lot of us who have studied social insects for a long time have never seen antennae used in that way,” explained Michael Goodisman, a professor in the Georgia Tech School of Biology and one of the paper´s other co-authors. “It´s incredible that they catch themselves with their antennae. This is an adaptive behavior that we never would have expected.”

Whereas this research has so far focused on understanding the principles behind how ants move in confined spaces, the results could have implications for future teams of small robots. It might be worth the spoiled picnics and ant bites.