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Posted on April 13, 2009 by  & 

Harvesting needed for robot flies

Robert Wood, an assistant professor of engineering and applied sciences at Harvard University has developed a revolutionary fabrication technique that allows engineers to make a range of very tiny parts for any kind of robot resulting in a life-size robotic fly. This tiny robot has a wingspan of three centimetres, weighs 60 milligrams and can generate nearly twice its weight in thrust which is almost on par with a real fly.
Designing a robotic insect is more complicated than simply shrinking a model airplane, however, because the aerodynamics of flight are entirely different on the scale of insects. Part of the challenge is that many systems contribute to the flight of a fly, including eyes specially attuned to perceiving motion and powerful muscles that drive the wings to generate unsteady aerodynamic forces, on which the fly's maneuverability depends. Most insects control their wings by adjusting the amplitude of their wing strokes, the angle of attack, and the tilt of their strokes through tiny muscles in the thorax. Flies even have special sensory organs, called halteres, that sense body rotations during flight. These features are all key to flies' remarkable ability to hover, fly upside down, and land on walls and ceilings. The researchers placed a great deal of importance on choice of materials, which ultimately had to be cheap and fairly easy to work with. Durability was less important, as they envisioned a robot that could be replaced for less than $10.
The robot fly is intended to perform rescue and reconnaissance operations in areas that humans cannot reach. For example, during rescue missions after earthquakes, thousands of paper clip-size flying robots could be dispersed throughout the collapsed buildings. The tiny robots would detect signs of life, perhaps by sniffing the carbon dioxide of survivors' breath or detecting the warmth of their bodies. And although some flies might smash into windows or get stuck in corners, others would make their way to the survivors, where they would perch and expend their remaining energy transmitting their findings to rescue workers. They may have onboard radio-frequency transmitters to communicate short, low-bandwidth chirps, to be picked up by receivers around the site. Even if 99 percent of the robots are lost, the search mission would still be a success.
Then there's the question of getting a power source onto the fly. A battery small enough to fit aboard a robotic fly will have a much higher surface-area-to-volume ratio than its macroscale counterpart, so a greater percentage of its mass will be the packaging. Wood expects that scaled-down versions of today's best lithium-polymer batteries will weigh about 50 mg, accounting for half the fly's weight, and will provide 5 to 10 minutes of flight. For more flight time the battery will need an increased energy density, the propulsion must be more efficient, or energy-harvesting techniques must be developed, perhaps by mounting tiny solar panels on the insect's back or converting the fly's vibrations into electric current.
Wood's ultimate goal is a fully autonomous robotic insect. He said "we predict that a fully autonomous robotic insect will be flying in laboratory conditions within five years. Five years beyond that, we could begin seeing these devices in our daily lives."
Source: Robert Wood
Image: Robotic fly. Source Flight Global
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