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Thread: Peregrine falcons are guided missiles

  1. #1
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    Peregrine falcons are guided missiles

    Laboratory Equipment magazine

    Peregrine falcons are known to be one of nature’s fastest predators, capable of diving through the air at speeds of up to 200 mph.

    Their impressive speed, “swooping” moves and accuracy in latching onto their prey mid-air has piqued the interest of researchers for decades. Until now, it was thought that peregrines’ aerial hunting method followed simple geometric rules, but a new study from Oxford University researchers now debunks that theory.

    The study results, published recently in PNAS, show that peregrine falcons actually use the same guidance law that missile engineers have developed to guide missiles to moving targets. The findings could be applied to the design of small, visually guided drones that take down other “rogue” drones in no-fly zones, according to the researchers.
    The researchers discovered that the attack trajectories are described by the same feedback law used by visually guided missiles – known as proportional navigation (PN) – but with a tuning optimized for their lower flight speed. Using PN, falcons can successfully collide with prey by tracking how the pathway between the falcon and the prey target is changing, rather than calculating the speed and direction of both the falcon and its prey.
    Link to journal and abstract
    Abstract

    The ability to intercept uncooperative targets is key to many diverse flight behaviors, from courtship to predation. Previous research has looked for simple geometric rules describing the attack trajectories of animals, but the underlying feedback laws have remained obscure. Here, we use GPS loggers and onboard video cameras to study peregrine falcons, Falco peregrinus, attacking stationary targets, maneuvering targets, and live prey. We show that the terminal attack trajectories of peregrines are not described by any simple geometric rule as previously claimed, and instead use system identification techniques to fit a phenomenological model of the dynamical system generating the observed trajectories. We find that these trajectories are best—and exceedingly well—modeled by the proportional navigation (PN) guidance law used by most guided missiles. Under this guidance law, turning is commanded at a rate proportional to the angular rate of the line-of-sight between the attacker and its target, with a constant of proportionality (i.e., feedback gain) called the navigation constant (N). Whereas most guided missiles use navigation constants falling on the interval 3 ≤ N ≤ 5, peregrine attack trajectories are best fitted by lower navigation constants (median N < 3). This lower feedback gain is appropriate at the lower flight speed of a biological system, given its presumably higher error and longer delay. This same guidance law could find use in small visually guided drones designed to remove other drones from protected airspace.
    There are links to the videos at the journal link.
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  2. #2
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    The ability to intercept uncooperative targets
    What a phrase. Love it. I bet that would be lovely in Latin, under the badge of some air defense squadron. (ETA: ok, maybe not. "A quad scuta facultatem palantes intercipiant" says Google)

    The description of the paper actually made me think of the work done by jet fighter computers, and the abstract's mention of video almost begs for a video with simulated HUD gunsight tracking.

    There are links to the videos at the journal link.

    Quote Originally Posted by Swift View Post
    There are links to the videos at the journal link.
    Those videos are wild!
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  3. #3
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    the lower feed back constant maybe due to prey changing course unpredictably.?
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    That was actually fun, but jeeze are they aggressive.
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  5. #5
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    It has been years since I came across a study on bats and how they tracked prey for mid-air interception so I may be wrong, but I'm pretty sure that the years old study I'm thinking of found that bats use the same method. It also really surprised the researchers.

    Okay, I'm pretty sure this is the study I was thinking of, Echolocating Bats Use a Nearly Time-Optimal Strategy to Intercept Prey.

    Some excerpts from the abstract . . .

    "Studies of target pursuit in animals, ranging from dragonflies to fish and dogs to humans, have suggested that they all use a constant bearing (CB) strategy to pursue prey or other moving targets. CB is best known as the interception strategy employed by baseball outfielders to catch ballistic fly balls. CB is a time-optimal solution to catch targets moving along a straight line, or in a predictable fashion-"
    "Echolocating bats rely on sonar to pursue and capture flying insects. The bat's prey may emerge from foliage for a brief time, fly in erratic three-dimensional paths before returning to cover. Bats typically take less than one second to detect, localize and capture such insects. We used high speed stereo infra-red videography to study the three dimensional flight paths of the big brown bat, Eptesicus fuscus, as it chased erratically moving insects in a dark laboratory flight room. We quantified the bat's complex pursuit trajectories using a simple delay differential equation. Our analysis of the pursuit trajectories suggests that bats use a constant absolute target direction strategy during pursuit. We show mathematically that, unlike CB, this approach minimizes the time it takes for a pursuer to intercept an unpredictably moving target. Interestingly, the bat's behavior is similar to the interception strategy implemented in some guided missiles."

  6. #6
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    "Studies of target pursuit in animals, ranging from dragonflies to fish and dogs to humans, have suggested that they all use a constant bearing (CB) strategy to pursue prey or other moving targets. CB is best known as the interception strategy employed by baseball outfielders to catch ballistic fly balls. CB is a time-optimal solution to catch targets moving along a straight line, or in a predictable fashion-"
    Now that you mention it Darrell, I recall the the work studying baseball outfielders.

    It actually makes a lot of sense that a wide variety of animals use the same strategy.
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