Insects to take the field from robotic birds?

The US NAV program was initiated by DARPA to develop a new class of air vehicles capable of indoor and outdoor operations. Employing biological mimicry at an extremely small scale this unconventional aircraft is designed to provide new military reconnaissance capabilities in urban environments. AV's NAV is designed to weigh no more than 10 grams and have the ability to carry a payload of up to 2 grams. AV's NAV team has already developed the Black Widow and Wasp MAVs for DARPA.

"Our Raven and Wasp III UAS began as early development programs similar to the NAV program, and now help protect the lives and enhance the operational effectiveness of warfighters and first responders," said John Grabowsky, AV executive VP and GM of unmanned aircraft systems. "The NAV program represents the early development of a revolutionary new class of UAS that could eventually provide valuable new capabilities to our customers," Grabowsky added.

US armed forces use AV's hand-launched UAS extensively for missions such as base security, route reconnaissance, mission planning, battle damage assessment and force protection. The US Army reported that its Ravens were flown for approximately 150,000 combat hours in 2007. AV has delivered over 9,000 small unmanned aircraft to date, including Raven, Wasp and Puma.

How Europe is working                                                
Courtesy: http://lis.epfl.ch/index.html?content=home.php
Europe is not trailing this scene and one of its most dedicated Laboratories of Intelligent Systems at Ecole Polytechnique Federale de Lausanne Current research project has the goal of  developing control strategies and  neuromorphic chips for autonomous microflyers capable of navigating in confined or cluttered areas such as houses or small built environments using vision as main source of information.

Flying in such environements implies a number of challenges that are not found in high-altitude, GPS-based, unmanned aerial vehicles (UAVs). These include small size and slow speed for maneuverability, light weight to stay airborne, low-consumption electronics, and smart sensing and control. We believe that neuromorphic vision chips and bio-inspired control strategies are very promising methods to solve this challenge.

The project is articulated along three, tightly integrated, research directions:
  1. Mechatronics of indoor microflyers (Adam Klaptocz, EPFL);
   2. Neuromorphic vision chips (Rico Möckel, INI);
   3. Insect-inspired flight control strategies (Antoine Beyeler, EPFL).

It plans to take inspiration from flying insects both for the design of the vision chips and for the choice of control architectures. Instead, for the design of the microflyers, we intend to develop innovative solutions and improvements over existing micro-helicopter and micro-airplanes.

Our final goal is to better understand the minimal set of mechanisms and strategies required to fly in confined environments by testing theoretical and neuro-physiological models in our microflyers.
                                              
Image Courtesy: http://medien.informatik.uni-ulm.de/abteilung/mitarbeiter/hermann.xml
The Dragonfly approach
A  group of European researchers believe that the key to making such a robot might lie in the dragonfly. Dragonflies are one of few creatures that utilise four independently controlled wings to fly, allowing them to hover, dart, glide, move backward, and change directions rapidly.

Looking to understand such abilities, scientists at the Royal Veterinary College, in England, and the University of Ulm, in Germany, have developed a robotic dragonfly to measure the current flows over and under the wings at different flap cycles.

While most of the dragonfly hovering scenarios were not efficient, the team found that if the lower wings are beating slightly ahead of the top wings, the double set of wings proves more efficient at generating lift, employing 22% less power to lift the same weight as a single pair.

"The one specific advantage you get in four wings is the maneuverability and ability to pick things out of the air and hover and dart around," says Jonathan How, a MIT professor working on flying robots but not involved in the dragon-
fly project. "It would be really amazing if we could build something that got
anywhere near that level of performance. If you can achieve the same lift at
a lower power, that's helpful."

Despite their potential advantages, small flying robots that mimic dragonflies' agility have not been successfully made, in part because of aerodynamic complexity around four wings, and  fabrication issues with small flying machines. However, studies of wing motion and air forces that reveal how dragonflies achieve their agility may enable roboticists to eventually build capable, swift flyers that use four wings.

To measure the air currents, the Ulm researchers immersed the 10cm tall robotic dragonfly in a tank filled with mineral oil and peppered with air bubbles. Two green lasers combined and reflected off the air bubbles as a high-speed camera took images 10 to 20 milliseconds apart indicating the aerodynamic lift forces created by the wings.  By comparing images, the scientists calculated the direction of flow for regions within the tank.

Web: http://www.avinc.com/
http://lis.epfl.ch/index.html?content=home.php
Source: http://www.technologyreview.com

Further reading: Bio-inspired flying robots
Jean-Christophe Zufferey, EPFL Press, 2008
Web: http://book.zuff.info/

Image Credit: Volker Steger