Micro air vehicle

Naval Air Weapons Station China Lake, California - The RQ-16 T-Hawk, a Micro Air Vehicle (MAV), flies over a simulated combat area during an operational test flight. The MAV is in the operational test phase with military Explosive Ordnance Disposal (EOD) teams to evaluate its short-range scouting capabilities.
A simulation screenshot of a "bumblebee-sized" MAV proposed by the U.S. Air Force in 2008[1]

A micro air vehicle (MAV), or micro aerial vehicle, is a class of miniature UAVs that has a size restriction and may be autonomous. Modern craft can be as small as 15 centimetres. Development is driven by commercial, research, government, and military purposes; with insect-sized aircraft reportedly expected in the future. The small craft allows remote observation of hazardous environments inaccessible to ground vehicles. MAVs have been built for hobby purposes,[2] such as aerial robotics contests and aerial photography.

Practical implementations

In January 2010, the Tamkang University (TKU) in Taiwan realized autonomous control of the flight altitude of an 8-gram, 20-centimeter wide, flapping-wing MAV. The MEMS Lab in the TKU has been developing MAVs for several years, and since 2007 the Space and Flight Dynamics (SFD) Lab has joined the research team for the development of autonomous flight of MAVs. Instead of traditional sensors and computational devices, which are too heavy for most MAVs, the SFD combined a stereo-vision system with a ground station to control the flight altitude,[3][4] making it the first flapping-wing MAV under 10 grams that realized autonomous flight.

In 2008, the TU Delft University in the Netherlands developed the smallest ornithopter fitted with a camera, the DelFly Micro, the third version of the DelFly project that started in 2005. This version measures 10 centimeters and weighs 3 grams, slightly larger (and noisier) than the dragonfly on which it was modeled. The importance of the camera lies in remote control when the DelFly is out of sight. However, this version has not yet been successfully tested outside, although it performs well indoors. Researcher David Lentink of Wageningen University, who participated in the development of previous models, DelFly I and DelFly II, says it will take at least half a century to mimic the capabilities of insects, with their low energy consumption and multitude of sensors—not only eyes, but gyroscopes, wind sensors, and much more. He says fly-size ornithopters should be possible, provided the tail is well designed. Rick Ruijsink of TU Delft cites battery weight as the biggest problem; the lithium-ion battery in the DelFly micro, at one gram, constitutes a third of the weight. Luckily, developments in this area are still going very fast, due to demand in various other commercial fields.

Ruijsink says the purpose of these craft is to understand insect flight and to provide practical uses, such as flying through cracks in concrete to search for earthquake victims or exploring radioactivity-contaminated buildings. Spy agencies and the military also see potential for such small vehicles as spies and scouts.[5]

Robert Wood at Harvard University developed an even smaller ornithopter, at just 3 centimeters, but this craft is not autonomous in that it gets its power through a wire. The group has achieved controlled hovering flight in 2013[6] as well as landings on and takeoffs from different overhangs in 2016[7] (both inside a motion tracking environment).

In early 2008 the United States company Honeywell received FAA approval to operate its MAV, designated as gMAV in the national airspace on an experimental basis. The gMAV is the fourth MAV to receive such approval. The Honeywell gMAV uses ducted thrust for lift, allowing it to takeoff and land vertically and to hover. It is also capable of "high-speed" forward flight, according to the company, but no performance figures have been released. The company also states that the machine is light enough to be carried by a man. It was originally developed as part of a DARPA program, and its initial application is expected to be with the police department of Miami-Dade County, Florida.[8]

In 2012, the British Army deployed the sixteen gram Black Hornet Nano Unmanned Air Vehicle to Afghanistan to support infantry operations.[9][10][11]

Practical limitations

Although there are currently no true MAVs (i.e., truly micro scaled flyers) in existence, DARPA has attempted a program to develop even smaller Nano Air Vehicles (NAVs) with a wingspan of 7.5 centimeters.[12] However, no NAVs meeting DARPA's original program specification were forthcoming until 2009 when AeroVironment demonstrated a controlled hovering of DARPA's flapping-wing NAV.[13]

Beyond the difficulties in developing MAVs, few designs adequately address control issues. The MAVs' small size makes teleoperation impractical because a ground station pilot cannot see it beyond 100 meters. An onboard camera allowing the ground pilot to stabilize and navigate the craft was first demonstrated in the Aerovironment Black Widow, but truly micro air vehicles cannot carry onboard transmitters powerful enough to allow for teleoperation. For this reason, some researchers have focused on fully autonomous MAV flight. One such device, which has been designed from its inception as a fully autonomous MAV, is the biologically-inspired Entomopter originally developed at the Georgia Institute of Technology under a DARPA contract by Robert C. Michelson.[14]

Given that MAVs can be controlled by autonomous means, significant test and evaluation issues continue to exist.[15][16]

Bio-inspiration

See also: Ornithopter
Bhargav Gajjar with sparrow hawk MAV and perching claws

A new trend in the MAV community is to take inspiration from flying insects or birds to achieve unprecedented flight capabilities. Biological systems are not only interesting to MAV engineers for their use of unsteady aerodynamics with flapping wings; they are increasingly inspiring engineers for other aspects such as distributed sensing and acting, sensor fusion and information processing. Recent research within the USAF has focused on development of bird like perching mechanism. A ground mobility and perching mechanism inspired from bird claws was recently developed by Bhargav Gajjar of Vishwa Robotics and MIT sponsored by US Air Force Research Laboratory [17]

Various symposia bringing together biologists and aerial roboticists have been held with increasing frequency since 2000[18][19] and some books[20][21][22] have recently been published on this topic. Bio-inspiration has been also used in design of methods for stabilization and control of systems of multiple MAVs. Researchers took inspiration from observed behaviors of schools of fish and flocks of birds to control artificial swarms of MAVs [23][24][25][26] and from rules observed in groups of migratory birds to stabilize compact MAV formations.[27][28][29][30][31]

See also

References

  1. ↑ US Air Force Flapping Wing Micro Air Vehicle - YouTube
  2. ↑ MAV multicopter hobby project "Shrediquette BOLT", http://shrediquette.blogspot.de/p/shrediquette-bolt.html
  3. ↑ Cheng-Lin Chen and Fu-Yuen Hsiao*, Attitude Acquisition Using Stereo-Vision Methodology, presented as Paper VIIP 652-108 at the 2009 IASTED Conference, Cambridge, UK, Jul. 13-15, 2009
  4. ↑ Sen-Huang Lin, Fu-Yuen Hsiao*, and Cheng-Lin Chen, Trajectory Control of Flapping-wing MAV Using Vision-Based Navigation, accepted to present at the 2010 American Control Conference, Baltimore, Maryland, USA, Jun. 30 - Jul. 2, 2010
  5. ↑ Bug-sized spies: US develops tiny flying robots
  6. ↑ Ma, K. Y., Chirarattananon, P., Fuller, S. B., & Wood, R. J. (2013). Controlled Flight of a Biologically Inspired, Insect-Scale Robot. Science, 340(6132), 603-607.
  7. ↑ Graule, Moritz A.; Chirarattananon, Pakpong; Fuller, Sawyer B.; Jafferis, Noah T.; Ma, Kevin Y.; Spenko, Matthew; Kornbluh, Roy; Wood, Robert J. (May 2016). "Perching and takeoff of a robotic insect on overhangs using switchable electrostatic adhesion". Science. 352 (6288): 978–982. doi:10.1126/science.aaf1092.
  8. ↑ Honeywell Wins FAA Approval for MAV, Flying Magazine, Vol. 135., No. 5, May 2008, p. 24
  9. ↑ Mini helicopter drone for UK troops in Afghanistan
  10. ↑ https://www.gov.uk/government/news/miniature-surveillance-helicopters-help-protect-front-line-troops
  11. ↑ "Mini helicopter drone for UK troops in Afghanistan". BBC. 3 February 2013. Retrieved 3 February 2013.
  12. ↑ program
  13. ↑ Benchergui, Dyna, “The Year in Review: Aircraft Design,” Aerospace America, December 2009, Volume 47, Number 11, American Institute of Aeronautics and Astronautics, p. 17
  14. ↑ Michelson, R.C., “Mesoscaled Aerial Robot,” Final Report under DARPA/DSO Contract Number: DABT63-98-C-0057, February 2000
  15. ↑ Michelson, R.C., “Test and Evaluation for Fully Autonomous Micro Air Vehicles,” The ITEA Journal, December 2008, Volume 29, Number 4, ISSN 1054-0229 International Test and Evaluation Association, pp. 367-374
  16. ↑ Boddhu, Sanjay K., et al. "Improved Control System for Analyzing and Validating Motion Controllers for Flapping Wing Vehicles." Robot Intelligence Technology and Applications 2. Springer International Publishing, 2014. 557-567.
  17. ↑ "Drone with legs can perch on tree branches and walk like birds".
  18. ↑ International Symposium on Flying Insects and Robots, Monte Verità, Switzerland, http://fir.epfl.ch
  19. ↑ Michelson, R.C., “New Perspectives on Biologically-Inspired MAVs (bio motivation rather than bio mimicry),” 1st US-Asian Demonstration and Assessment of MAV and UGV Technology Conference, Agra India, 10–15 March 2008
  20. ↑ Ayers, J.; Davis, J.L.; Rudolph, A., eds. (2002). Neurotechnology for Biomimetic Robots. The MIT Press. ISBN 0-262-01193-X.
  21. ↑ Zufferey, J.-C. (2008). Bio-inspired Flying Robots: Experimental Synthesis of Autonomous Indoor Flyers. EPFL Press/CRC Press. ISBN 978-1-4200-6684-5.
  22. ↑ Floreano, D.; Zufferey, J.-C.; Srinivasan, M.V.; Ellington, C., eds. (2009). Flying Insects and Robots. Springer-Verlag. ISBN 978-3-540-89392-9.
  23. ↑ Saska, M.; Vakula, J.; Preucil, L. Swarms of Micro Aerial Vehicles Stabilized Under a Visual Relative Localization. In ICRA2014: Proceedings of 2014 IEEE International Conference on Robotics and Automation. 2014.
  24. ↑ Saska, M. MAV-swarms: unmanned aerial vehicles stabilized along a given path using onboard relative localization. In Proceedings of 2015 International Conference on Unmanned Aircraft Systems (ICUAS). 2015
  25. ↑ Bennet, D. J.; McInnes, C. R. Verifiable control of a swarm of unmanned aerial vehicles. Journal of Aerospace Engineering, vol. 223, no. 7, pp. 939–953, 2009.
  26. ↑ Saska, M.; Chudoba, J.; Preucil, L.; Thomas, J.; Loianno, G.; Tresnak, A.; Vonasek, V.; Kumar, V. Autonomous Deployment of Swarms of Micro-Aerial Vehicles in Cooperative Surveillance. In Proceedings of 2014 International Conference on Unmanned Aircraft Systems (ICUAS). 2014.
  27. ↑ Saska, M.; Kasl, Z.; Preucil, L. Motion Planning and Control of Formations of Micro Aerial Vehicles. In Proceedings of The 19th World Congress of the International Federation of Automatic Control. 2014.
  28. ↑ Barnes, L.; Garcia, R.; Fields, M.; Valavanis, K. Swarm formation control utilizing ground and aerial unmanned systems, in IEEE/RSJ International Conference on Intelligent Robots and Systems. 2008.
  29. ↑ Saska, M.; Vonasek, V.; Krajnik, T.; Preucil, L. Coordination and Navigation of Heterogeneous UAVs-UGVs Teams Localized by a Hawk-Eye Approach. In Proceedings of 2012 IEEE/RSJ International Conference on Intelligent Robots and Systems. 2012.
  30. ↑ Saska, M.; Vonasek, V.; Krajnik, T.; Preucil, L. Coordination and Navigation of Heterogeneous MAV–UGV Formations Localized by a ‘hawk-eye’-like Approach Under a Model Predictive Control Scheme. International Journal of Robotics Research 33(10):1393–1412, September 2014.
  31. ↑ No, T.S.; Kim, Y.; Tahk, M.J.; Jeon, G.E. (2011). Cascade-type guidance law design for multiple-uav formation keeping. Aerospace Science and Technology, 15(6), 431 – 439.

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