Owl may be Inspiration for Aerial Stealth Robots

Owl may be Inspiration for Aerial Stealth Robots

18 August 2015 |

As a Roboticist when we think about owl, our focus goes on its night vision capability. Inspired from it we invented lots of night vision sensors like thermal imager and Infrared sensor by which we can see in dark nights. Nowadays almost all mobile robots are using these night vision sensors to work in dark nights.

But now researchers found another positive point in Owl – “A unique ability to fly silently” means Stealth technique of flying. The Owl’s feathers are naturally designed such a way that it attenuates more flight vibration noise in compare to other birds like eagle and pigeon.

Also Read: Sea Lion Inspired Research for Underwater Stealth Robotics

Owls generate noise in both gliding and flapping flight at very low frequencies below 2 kHz, which is out of the our hearing range. This quiet flight behaviour has long been of interest to engineers, with the purpose to apply owl’s noise-reducing mechanisms to technical applications.

When a bird flies, the sources of noise are mechanical noise generated by feathers at flapping time and aerodynamic noise generated by air disturbance around the feathers.

This research was mainly focused on how do owls suppress the noise?

Owl’s flight generally consists of an initial flapping phase followed by a gliding phase and a short flapping during touchdown. Golden eagle involves a same flight style as the long-eared owl, but its size is larger than the long-eared owl. Pigeon is a typical flapping flight bird which differs from the long eared owl and has a smaller size than the owl. Both of the golden eagle and the pigeon do not have the silent flight ability.

To investigate the noise reducing ability of owl, researchers from Dalian University of Technology, China carried out a comparative study of vibration attenuation behaviour of primary remex with lateral branches from the long-eared owl (a silent flying bird), golden eagle and pigeon (two noisy flying birds). And they published the result of their work in “Bioinspired, Biomimetic and Nanobiomaterials” Journal.

To know the mystery behind the owl’s noise reduction ability researchers investigated electron microscope images of the barbs and found that the design structure of owl’s feathers is different and unique from others which is the main cause of noise reduction.

Scanning electron microscope images of the barbs. (a) Long-eared owl feather barb. (b) Golden eagle feather barb. (c) Pigeon feather barb. Line with double arrowheads refers to the length of the pennulum (Image: paper)

Researchers concluded that for the long-eared owl, mechanical noise caused by wing vibration and feather friction would effectively be suppressed due to its superior damping performance and aerodynamic noise suppression occurs due to the comb-like structures on owl feather

Aerial robots are one of the potential application areas for the operations where stealth is required.

  • Explore further: CROC: Inchworm Inspired Climbing Robot
  • Reference: “Vibration attenuation performance of long-eared owl plumage” Bioinspired, Biomimetic and Nanobiomaterials, Volume 4, Issue 3, April 2015 pages 187 –198; Jiali Gao,  Jinkui Chu,  Haixin Shang, Le Guan [Paper]

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