By Karin Jegalian

BIOLOGY INSPIRES TECHNOLOGY + DESIGN

Maryland researchers designed a mobile robot (left) with a guidance system based on the echolocation ability of the common brown bat. Photo by John T. Consoli.

Human engineers have built all sorts of machines—cars, helicopters, robotic vacuum cleaners—that resemble nothing found in nature. Most engineers don’t give much thought to biology, whose revelations can seem haphazard compared with the precision of physics and math. Despite the long-standing separation between the fields, some engineers realize they can learn a lot from nature.

A cadre of researchers at the University of Maryland, especially a group specializing in flight and navigation, is turning to biology for inspiration. After all, evolution has had billions of years to craft such engineering masterpieces as birds that stay aloft for days, bats that navigate in the dark, maple tree seeds that drift gently to the ground, and the seemingly humble fruit fly, which can pilot itself gallantly in the face of wind gusts without knocking into walls or telephone poles.

Faculty in the A. James Clark School of Engineering glean new scientific knowledge by closely observing nature, studying the intricate wing structure of a Japanese maple samara (inset) and the sensory ability of a fruit fly’s compound eye.

J. Sean Humbert, assistant professor of aerospace engineering, studied neurobiology as well as engineering in graduate school. He and the students in his bustling lab take cues from biology as they build robots and unmanned aerial vehicles, or UAVs, that can navigate themselves.

“You want to be able to fly in the urban clutter,” Humbert explains. “If you see a telephone wire ahead of you, you duck,” Humbert says, but UAVs don’t yet. To build better versions, Humbert wants to understand “the sensory architecture” in animals like fruit flies and how their sensory systems integrate with the animals’ impressive flight mechanics.

This spring, the Army Research Laboratory selected a team headed by Humbert and Inderjit Chopra, professor of aerospace engineering, to lead a nationwide collaboration to develop miniature autonomous vehicles that can give soldiers’ awareness of complex terrain before they enter it. The researchers are working to develop different kinds of robots for different contexts, including tiny vehicles that can flap their wings and small ground robots that can crawl over terrain and jump over mud puddles to map the ground.

Physics of Light Flight

Humans have a good track record of designing aerial vehicles that are large and heavy, but nature is better at designing aerial vehicles that are small and light. Aerospace engineers at the university want to understand whether some methods of flying are indeed superior at smaller scales. For example, flapping wings may allow more control than rotors do.

In a small wind tunnel in Humbert’s lab, cameras record flies’ wing motions and rotations using high-speed video. Flies maneuver by making subtle adjustments to their rapidly flapping wings, whose dynamics scientists are only beginning to understand.

Darryll Pines, professor and chair of aerospace engineering, says that in five years, researchers should know much more about the aerodynamics of flight on a small scale, guided by examples in nature. The university “has some of the best researchers in the nation to solve these problems,” Pines says.

Pines and the members of his lab have long worked to improve the design of rotary systems. One set of small, unmanned vehicles they have designed is modeled on specialized leaves, known as samara, which spread the seeds of maple trees and other plants.

“The samara has the lowest descent rate known for anything of the same weight and size,” which helps the seeds disperse, Pines explains. Pines and his collaborators have been developing ways to power and steer vehicles inspired by samaras. The team is also studying the inner structure of the specialized leaves to understand the mechanics behind their flexibility and aerodynamics.

Researchers in aerospace engineering are also taking inspiration from soaring birds. James Hubbard, a professor of aerospace engineering who works closely with NASA, has been inspired by albatrosses, which can circumnavigate the globe in a month, flying day and night, even while resting mid-flight. Near the ocean in Virginia, Hubbard says, “I noticed that there were birds that never seemed to flap their wings. I became very interested in knowing if we could design a vehicle that could exploit atmospheric energy and stay up basically 24-7.”

Jared Grauer ’05, M.S. ’07, a doctoral student in flight dynamics and control, studies the wing structure of large birds. Maryland researchers are particularly interested in the flight dynamics of the albatross (inset), which can travel extremely long distances while expending minimal energy.

Chopra and his research group also build flapping- wing devices inspired by insects and birds, as well as rotor-powered devices of all sizes. Even for rotor-powered vehicles, Chopra says that biology can provide inspiration. He and his students study how subtle refinements to rotor shape affect air movement, and they are designing flexible rotors that flap slightly as they spin.

Sensory Systems

Humbert is working with Timothy Horiuchi, associate professor of electrical and computer engineering, to develop new ways for robots to see and steer, using a combination of vision and sonar. Horiuchi also collaborates closely with Cynthia Moss, professor of psychology, and P.S. Krishnaprasad, professor of electrical and computer engineering, all members of Maryland’s Institute for Systems Research. Their joint research focuses on another type of flight control, echolocation in bats. Echolocating bats use the bouncing, or echoing, of their voices to avoid obstacles and find insect prey. They also use the fine hairs on their wings to sense air turbulence.

Timothy Horiuchi (above) collaborates with faculty from across disciplines to develop new engineering systems, including bat-inspired navigation devices on small, unmanned aerial vehicles.

Moss says her interest in bats is rooted in the more general problem of how creatures use “active perception” to respond to their environment as they move rapidly through it. Relying on its vocalizations, an insect-eating bat can intercept a far-off mosquito. In Moss’s lab, bats distinguish a distant bead that has a groove oriented vertically from a bead with its groove oriented horizontally.

Engineering can be used to develop quantitative rules for understanding bat behavior, Krishnaprasad explains, as well as offer the possibility of applying insights gleaned from bats in robotics and navigation systems.

Moss’s team found that bats can easily navigate through a hole in a fine mist net to eat a worm, increasing their rate of vocalization when they get close to objects. Her team has also created artificial forests in the lab to see how bats use echolocation to navigate. “I couldn’t ask for a better problem,” says Krishnaprasad, about trying to extract the mathematical rules that govern bat behavior. What Humbert has found about flies applies to bats, birds and plants, as well.

“The deeper we probe into these insects, the more elegant and wonderful their systems are,” he says “They’re so robust compared to anything we have built. The existence proof is there.” If nature has created machinery that is so light, energy-efficient, ingenious and effective, their existence is proof that engineers can too. TERP

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