Cracking flight's mysteries: It's a bird, it's a plane, it's a microrobot

Sep 06, 2010 By Steve Bradt
Associate Professor of Electrical Engineering Rob J. Wood (left) and graduate student Pratheev S. Sreetharan are working on miniature flying vehicles that could someday be used to probe environmental hazards, forest fires, and other challenges too perilous for people. Image: Justin Ide

(PhysOrg.com) -- Engineers at Harvard University have created a millionth-scale automobile differential to govern the flight of minuscule aerial robots that could someday be used to probe environmental hazards, forest fires, and other challenges too perilous for people.

Their new approach is the first to passively balance the encountered by these miniature flying devices, letting their wings flap asymmetrically in response to gusts of wind, structural damage, and other real-world impediments.

“The drivetrain for an aerial shares many characteristics with a two-wheel-drive automobile,” said lead author Pratheev S. Sreetharan, a graduate student in Harvard’s School of Engineering and Applied Sciences. “Both deliver power from a single source to a pair of wheels or wings. But our 'PARITy differential' generates torques up to 10 million times smaller than in a car, is 5 millimeters long, and weighs about one-hundredth of a gram — a millionth the mass of an automobile differential.” PARITy stands for passive aeromechanical regulation of imbalanced torques.

High-performance aerial microrobots, such as those that Harvard scientists describe in the Journal of Mechanical Design, could ultimately be used to investigate areas deemed too dangerous for people. Scientists at institutions including the University of California, Berkeley, the University of Delaware, the University of Tokyo, and Delft University of Technology in the Netherlands are exploring aerial microrobots as cheap, disposable tools that might someday be deployed in search-and-rescue operations, agriculture, environmental monitoring, and exploration of hazardous environments.

Harvard's 'PARITy differential' for MAVs

To fly successfully through unpredictable environments, aerial microrobots — which resemble insects, nature’s nimblest fliers — have to negotiate conditions that change second by second. Insects usually accomplish this by flapping their wings in unison, a process whose kinematic and aerodynamic basis remains poorly understood.

Sreetharan and his co-author, Robert J. Wood, recognized that an aerial microrobot based on an insect did not have to contain complex electronic feedback loops to control wing positions precisely.

“We’re not interested so much in the position of the wings as the torque they generate,” said Wood, an associate professor of electrical engineering at Harvard. “Our design uses ‘mechanical intelligence’ to determine the correct wing speed and amplitude to balance the other forces affecting the robot. It can slow down or speed up automatically to correct imbalances.”

Sreetharan and Wood found that even when a significant part of an aerial microrobot’s wing was removed, the self-correction engendered by their PARITy drivetrain allowed the device to remain balanced in flight. Smaller wings simply flapped harder to keep up with the torque generated by an intact wing, reaching speeds of up to 6,600 beats per minute.

The Harvard engineers say their passive approach to regulating the forces generated in flight is preferable to a more active approach involving electronic sensors and computation, which would add weight and complexity to devices that need to be as small and as lightweight as possible. Current-generation aerial microrobots are about the size and weight of many insects, and even make a similar buzzing sound when flying.

“We suspect that similar passive mechanisms exist in nature, in actual insects,” Sreetharan said. “We take our inspiration from biology, and from the elegant simplicity that has evolved in so many natural systems.”

Explore further: Minimally invasive surgery with hydraulic assistance

Related Stories

Micro flying robots can fly more effectively than flies

Aug 01, 2009

There is a long held belief among engineers and biologists that micro flying robots that fly like airplanes and helicopters consume much more energy than micro robots that fly like flies. A new study now shows ...

Flies Don't Think Much Of Turning (w/ Video)

Apr 02, 2010

The next time a fly dodges your swatter, take a moment to appreciate how maneuverable these little pests are. Fruit flies can make a complete U-turn in one-tenth of the time it takes you to blink.

Artificial butterfly in flight and filmed (w/ Video)

May 20, 2010

A group of Japanese researchers, who publish their findings today in Bioinspiration & Biomimetics, have succeeded in building a fully functional replica model - an ornithopter - of a swallowtail butterfly, and they have f ...

Recommended for you

Desktop device to make key gun part goes on sale in US

6 hours ago

The creator of the world's first 3D plastic handgun unveiled Wednesday his latest invention: a pre-programmed milling machine that enables anyone to easily make the core component of a semi-automatic rifle.

Minimally invasive surgery with hydraulic assistance

12 hours ago

Endoscopic surgery requires great manual dexterity on the part of the operating surgeon. Future endoscopic instruments equipped with a hydraulic control system will provide added support during minimally ...

Analyzing gold and steel – rapidly and precisely

14 hours ago

Optical emission spectrometers are widely used in the steel industry but the instruments currently employed are relatively large and bulky. A novel sensor makes it possible to significantly reduce their size ...

More efficient transformer materials

14 hours ago

Almost every electronic device contains a transformer. An important material used in their construction is electrical steel. Researchers have found a way to improve the performance of electrical steel and ...

Sensor network tracks down illegal bomb-making

14 hours ago

Terrorists can manufacture bombs with relative ease, few aids and easily accessible materials such as synthetic fertilizer. Not always do security forces succeed in preventing the attacks and tracking down ...

Miniature camera may reduce accidents

14 hours ago

Measuring only a few cubic millimeters, a new type of camera module might soon be integrated into future driver assistance systems to help car drivers facing critical situations. The little gadget can be ...

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

el_chief
not rated yet Sep 06, 2010
How about a video?
maxcypher
not rated yet Sep 06, 2010
Science in it's most elegant form, imho. But then, I'm partial to bio-mimetic systems and this device has that sort of unmanaged efficiency one finds in nature.
Shootist
1 / 5 (1) Sep 07, 2010
Cracking flight's mysteries: It's a bird, it's a plane, it's a microrobot


I prefer microbot. Thank you very much.