Charged Magazine

Tag: birds

  • Insect robots: How do they fly?

    Insect robots: How do they fly?

     

    “How do airplanes stay afloat?”

    “The same way a bird stays afloat.”

    When we give that answer to a kid, we fondly realize the connection between nature’s creatures and machines, and that the nature influenced creation of many machines from time to time. That is why the Wright brothers spent a great deal of time observing birds in flight and realized that when birds soared into the wind, the air flowed over the curved surface of their wings, and thus generated lift which helps them stay in flight. They noticed the wings of birds minutely, and realized that they change the shape of the wings to turn and maneuver, and thus flaps and stabilizers were born in the airplane wings. In a similar fashion, various insects and birds have influenced designs of many machines for their structural and aerodynamic ability. These creatures not only helped design the structural and aerodynamic systems of large machines, but attracted considerable attention from scientists and engineers for small-scale robots. Today we deep dive into the world of small robots and how they fly!

    Insects were the first organisms on Earth to take to the skies – estimates on the origin of insect flight range from ~320 to ~400 million years ago (Misof et al., 2014). That is a long, long time before vertebrates achieved this feat. Over time, insects mastered their flying ability, and achieved great perfection in speed, agility, and grace in the air. By design, insects such as hover flies and birds such as hummingbird have remarkable abilities to hover in the air, as well as being able to perform aerobatic maneuvers such as sideways or backward flying. The technique that they use is called a flapping wing motion. This remarkable ability is a key in the design of small-scale aircraft for surveillance or reconnaissance. Traditionally, engineers designed a medium to large scale aerodynamic vehicle with traditional mechanical linkage systems (Van Breugel et al., 2008). However, when it comes to an unmanned small-scale aerial vehicle (or even micro-scale that mimics the size of an actual small insect such as a hover fly), one of the key challenges in traditional designs was that the flapping-wing action was not stable because of the power and weight ratio that needs to be achieved to match the hovering and flying abilities of the insects and birds observed in nature.

    Historically, there have been a number of research efforts that focused on the mechanical and structural aspects of a small-scale flying robot design. One such project was the Entomopter project in Georgia Tech (Michelson et al., 1998). The researchers used a chemical muscle to produce linear actuation strain. Two sets of rigid wings (front and back) were placed, and chemical muscle actuated them. Other traditional designs of small-scale flying robots used gears and links for the movements needed for of an airborne vehicle.

    How do the “insect” robots get up in the air?

    In order to achieve a flapping action in-flight to gain altitude, sweeping and the pitching motions are needed to be achieved. The current design is set up to exploit resonant properties, as exhibited by flying insects, to reduce the energy expenditure and to provide amplitude amplification for the wing sweeping motion (Bolsman, 2010). Design objective for a small-scale flying machine is to reproduce a reference motion based on the kinematics of insects. Insects and birds perform wing flapping and adjustments of the body orientation in order to control speed, altitude and orientation of the flight. As shown in the figure below, to transfer this analogy to a micro-robot, the sweeping motion of the wings are emulated as a steady-state motion. The details of a control system can be found in advance literature (Bolsman, 2010). However, in simple terms, the design takes into account a constant resonance frequency, and a maximum wind sweeping stroke. As the stroke increases (shown by the extreme lines in the figure), the wings generate lift. The mass of the device (as in an insect) is centered towards the geometric center of the device, resulting in maximum possible stability. This is the stage where the robots get airborne and continue hovering.

    Lift: Flapping wing motion with sweeping stroke

    How do the “insect” robots move in the air?

    The hovering is the first state of condition that the robots achieve, similar to an insect. The figure above shows a simple two wing device. Each wing is designed to have independent controls to change flapping In order to change the direction to left or right, so that each wing is capable of having a different sweeping motion. This inevitably creates a sweeping motion that are not equal in each wing, and results in a rotation in the direction of the difference. An insect performs these exact same maneuvers to create a rotational motion for left-right (rolling) movement.

    As shown in the figure, the center position holds the center of mass for the whole assembly. As such, changing the center position of the sweeping motion will change the direction of flight as well. This is performed by shifting the positions of the effective centers of pressure of the left and right wings. This invariably creates a backward motion (or pitch), and more power from the device’s power source provides a required forward motion while maintaining the achieved altitude.

    How strong are these “insect” robots?

    A simple model of a small-scale flying robot has been described here to depict the fundamentals that are derived from an insect or a small bird for flapping motion design. A fully fledged flying micro robot has more control systems that are able to achieve a full range of motions if needed, with more complicated actuations that are associated with multiple wings and wing rotations. In addition, structural integrity is also a key factor which, surprisingly, is also derived from insects. One of the most fascinating and extraordinary creatures in earth are ants, they can carry objects several times of their body weight. Ant’s neck has a very sturdy construction by nature, because of the fact that they lift the large weights with their mouth, and the load is transferred through the neck. Researchers found from models that an ant’s neck can withstand loads of about 5,000 times the ant’s body weight! (Nguyen, 2012). This design is also simulated to be able to provide the micro robots a sturdy yet very lightweight construction, a critical requirement for such a device.

    Ultra-light, small scale robots are in use for surveillance, military operations, rescue missions, medical sector, hazardous material test/retrieval, and many other scenarios. We will continue to see the marvelous development of these micro machines, inspired by the insects and small birds around us, while pondering over the question: “how birds fly?”

    References:

    1. Bolsman, C. T. (2010). Flapping wing actuation using resonant compliant mechanisms: An insect-inspired design.
    2. Van Breugel, F., Regan, W., & Lipson, H. (2008). From insects to machines. IEEE robotics & automation magazine, 15(4), 68-74.
    3. Misof, B., Liu, S., Meusemann, K., Peters, R. S., Donath, A., Mayer, C., … & Niehuis, O. (2014). Phylogenomics resolves the timing and pattern of insect evolution. Science, 346(6210), 763-767.
    4. Michelson, R. C. (2000). S. Patent No. 6,082,671. Washington, DC: U.S. Patent and Trademark Office.
    5. Michelson, R. C., & Reece, S. (1998, March). Update on flapping wing micro air vehicle research-ongoing work to develop a flapping wing, crawling entomopter. In 13th Bristol International RPV/UAV Systems Conference Proceedings, Bristol England(Vol. 30, pp. 30-1).
    6. Nguyen, V. N. (2012). Development of a Finite Element Model of an Ant Neck Joint for Simulation of Tensile Loading(Doctoral dissertation, The Ohio State University).
  • Bad @ss Birds

    Bad @ss Birds

    I didn’t realize that birds were cool until I was a senior in high school (4 whole years ago). Just to be clear, this article is talking about the kind of bird that flies in the air, not the electric scooter that Georgia Tech students ride to class when they’re late. Ornithology is the study of birds, and I was lucky enough to take a class in high school that let me learn about them hands on. I’ve included some pictures at the end of experiences I’ve had with birds, but first, here are some of my favorite, more exotic, birds.

    Cuckoo Birds:

    Cuckoos are parasitic birds that lay their eggs in the nests of a different bird. The host can range depending on the location of the cuckoos and the specific cuckoo species, but most parasitic birds tend to pick hosts who are insectivores in order for their offspring to have a high protein diet (Payne).

    After the cuckoo lays its egg in the hosts nest, several events can occur. In some species of cuckoos, the cuckoo will hatch before the hosts eggs. This young cuckoo will then take the eggs of the host bird one at a time and eject them from the nest using its back. This allows the cuckoo nestling to receive all the attention, and food, from it’s host instead of splitting it with other nestlings. Other species of cuckoo won’t eject the hosts eggs, and the two species will be raised together by the host (Rothstein).

    Cuckoos have some mechanisms to prevent suspicion from their host. Cuckoo’s eggs tend to mimic the eggs of their host in appearance and size, and the nestlings will tend to have similar feeding habits to their host. When the host’s nestling and the cuckoo are reared together, the young tend to resemble their nest mates at the beginning then grow significantly larger than their nestlings and possibly even larger than their host parents (Rothstein).

    Pictured below is a cuckoo nestling ejecting other eggs from the host’s nest, and a cuckoo nestling being fed by its, much smaller, host parent.

    Photographer Unknown
    https://www.flickr.com/photos/internetarchivebookimages/14729384096/in/photostream/


    Photo by Per Harald Olsen
    https://commons.wikimedia.org/wiki/File:Reed_warbler_cuckoo.jpg

    Bower Birds:

    Bower birds have an aesthetic mating ritual. Male bower birds build intricate structures, called bowers, decorated with colored objects to impress a female bower bird. The bowers are created with twigs, and the objects used to decorate them can range from fruit and flowers to shells or grass. Birds near human contact will sometimes use flashy man-made pieces like jewelry or glass. The objects will be set in piles around the bower for the female to inspect. In at least one species of bower birds, the males will decorate their bowers with colors matching that of the intended female (Marshall).

    The bower isn’t the only part of the birds’ mating ritual. The female will watch the bower being built and the collection of objects for multiple months. During this time the male displays dances and mimics calls of other birds. When there’s enough food in the environment for a female bower bird to rear young, she can mate with the male. The female then leaves to create a nest and raise the young without the help of the male. The male can stay at its bower and attempt to mate with other females. It’s not restricted to mating once per season (Marshall).

    Below are two pictures of bowers each decorated with unique objects.


    Photo by Joseph C Boone
    https://en.wikipedia.org/wiki/Satin_bowerbird#/media/File:Satin_Bowerbird_at_his_bower_JCB.jpg


    Photo by Allan Henderson
    https://www.flickr.com/photos/88019192@N00/35514986355

    Kea:

    Kea, sometimes referred to as the sheep killers, are a native parrot of New Zealand. They’ve been protected by the New Zealand Wildlife Act for several decades, but many people find them to be a nuisance because of their curiosity. Human machines and buildings can be damaged or destroyed by the Kea’s sharp beaks and inquisitive attitudes (Brejaart).

    Slightly after sheep were introduced to New Zealand, the kea received a reputation for killing even though early numbers suggested that less than 5% of sheep were affected by the parrot. The government and private citizens established bounties in the late 1800s requesting kea’s beaks and heads, and these bounties continued until 1971 by which time an estimated 150 thousand keas were killed. Many researchers suggest that the death of sheep by non-kea causes were attributed to kea which lead to their villainous reputation (Brejaart).

    So how does a bird kill a sheep? Keas are known to land on a sheep’s back before picking at the outer wool until reaching flesh. They feed on the sheep while the animals are still alive, but the ultimate cause of death for the sheep would be blood poisoning or the like (Brejaart).

    Kea don’t just feed on live stock. In fact, a majority of their diet when under observation in Craigieburn Forest Park consisted of nuts and fruit (Brejaart). Below is a picture of a Kea, but if you would like to see something more graphic, look up ‘Kea feeding on Sheep’.


    The Kea. Photo by Bernard Spragg
    https://www.flickr.com/photos/volvob12b/9119203963

    Butcher Birds:

    Butcher birds are another species with an especially interesting feeding habit. They take their prey which ranges from small fledglings to insects and kill them using tools before consumption. Some of their anatomy resembles that of other meat consuming birds including their beak, but they lack the talons to physically pull their food apart. This is where their unique actions come into play (Beal and Waldo).

    Butcher birds take their prey and wedge it into the forks of branches (Marshall). This allows it to kill its prey or hold the prey in place while the bird pulls it apart with its beak. The most common prey are insects like grasshoppers and crickets with beetles coming in second. Depending on the species, the consumption of vertebrate (including birds, reptiles, and mammals) can range from 12% to 28% of prey (Beal and Waldo).

    In times of plenty, some researchers suggest that the birds store extra food on sharp branches. The Australian counter part of the pied butcher bird is the Loggerhead shrike which impales its prey on wire and branches (Beal and Waldo).

    Pictured below is a pied butcher bird, and you can also look up more graphic photos of their feeding habits.


    Photo by Gail Hampshire
    https://commons.wikimedia.org/wiki/File:Pied_Butcherbird._Cracticus_nigrogularis_(15207948764).jpg

    Moa:

    Moas, sometimes referred to as the elephant bird, are a large flightless bird ranging in weight from 45 lbs to 550 lbs. Unfortunately, they went extinct after Polynesian colonists arrived in New Zealand. Besides their incredible size, Moas are interesting because of the impact they had on natural scientists and their incredibly fast extinction after humans were introduced to their environment (Anderson).

    Early scientists heard tales of moas ranging in height to about 16 and a half feet, and they constructed the fossils found to support these myths. Moas actually range up to 8 feet tall, which is still a significant height. Research also shows that the birds were wingless (Anderson).

    Some people say that the moas have been romanticized through the ages, but you can decide that for yourself. Below is a drawing of what the moas looked like before their extinction.


    Picture by Joseph Smit
    https://commons.wikimedia.org/wiki/File:Giant_moa.jpg

    Pictures of me!

    This is me when we took a red shouldered hawk to falcon. This means that we took the red shouldered hawk to a forest and released it—watching as it attempted to catch squirrels with its talons. Fun fact: you can use any bird of prey to falcon.

    This picture is from when we dissected crows in the lab! It freaked me out a little at first, but once I opened the crow, it was really interesting.


    Blue birds make their nests in holes, so we had blue bird boxes around our campus. As a class, we would go around and periodically count the number of eggs in each box, and eventually we got to see the fledglings. It’s untrue that if you hold a baby bird or an egg that the mother will never come back.

    Citations:

    Anderson, Atholl. “Interest in Moas.” Prodigious Birds: Moas and Moa-Hunting in New Zealand, Cambridge University Press, 2003, pp. 2–3. https://books.google.com/books?hl=en&lr=&id=-Oo_kFo09VEC.

    Beal, Foster and Waldo L. McAtee. “Southern Butcher Bird.” Food of Some Well-Known Birds of Forest, Farm, and Garden, U.S. Dept. of Agriculture, 1922, pp. 29–32, https://books.google.com/books?hl=en&lr=&id=OewYAAAAYAAJ.

    Brejaart, Ria. “Diet and Feeding Behaviour of the Kea (Nestor Notabilis).” Diet and Feeding Behaviour of the Kea (Nestor Notabilis). 1998. Lincoln University, PhD disserataion.

    Marshall, A. J. “Bower-Birds.” Biological Reviews, vol. 29, no. 1, Feb. 1954, pp. 1–45. doi:10.1111/j.1469-185x.1954.tb01395.x.

    Marshall, David. “Stray Feathers: Feeding of Butcher-Birds.” The EMU, vol. 47, July 1947, pp. 68–69., www.publish.csiro.au/MU/pdf/MU947054r.

    Payne, Robert B. “The Ecology of Brood Parasitism in Birds.” Annual Review of Ecology and Systematics, vol. 8, no. 1, Nov. 1977, pp. 1–28., doi:10.1146/annurev.es.08.110177.000245.

    Rothstein, Stephen I. “A Model System for Coevolution: Avian Brood Parasitism.” Annual Review of Ecology and Systematics, vol. 21, 1990, pp. 481-508., doi:10.1146/annurev.es.21.110190.002405