University of Oxford researchers, Dr Caroline Brighton and Prof Graham Taylor, used high-speed cameras to capture the flight trajectories of five captive-bred Harris’ Hawks during 50 flights against an erratically-manoeuvring artificial target. The findings have applications to the design of drones for pursuing and capturing rogue drones in cluttered environments.
Researchers conducted a study and found that Harris’ Hawks use a mixed guidance law, in which their turn rate is determined by feeding back information on the angle between the direction to their target and their current flight direction, together with information on the rate at which the direction to their target is changing. And according to researchers this mixed guidance law reduces the risk of overshoot in the close pursuits to which hawks are adapted, but would produce an inefficient flight path if used in the long-range interception behaviours of falcons.
Dr Brighton said: ‘We filmed our hawks flying after a dummy bunny, which was an artificial target that we towed at speed around a series of pulleys laid out to produce an unpredictable course. Using video reconstruction techniques to measure the 3D trajectory of the hawk and its target, we then ran a computer simulation to see how closely the hawk’s attack behaviour was modelled by different kinds of guidance law.’
Researchers used four high-speed cameras recording at 250 Hz to reconstruct the three-dimensional (3D) flight trajectories of captive-bred Harris’ Hawks Parabuteo unicinctus during 50 flights against an erratically manoeuvring artificial target. The target comprised a food lure (a rabbit), which was towed at speed around a series of pulleys to create a sequence of zigzagging turns that we randomised on each trial to prevent the hawks from learning the course. The speed of the lure was adjusted continuously by the experimenter (median lure speed: 7.0 m s−1; interquartile range, IQR: 9.7 − 4.1 m s−1) to keep it ahead of the hawk until the moment of capture.
Prof Taylor commented: ‘Last year’s Gatwick incident showed just how far we are from being able to remove rogue drones quickly and safely from a large open space, let alone the cluttered airspace of an urban environment. Hawks are masters of close pursuit through clutter, so we think they have a thing or two to teach us about how to design a new kind of drone that can safely chase down another.’
Conclusions presented by the research discussed how the structure and tuning of the hawks’ mixed guidance law relates to their typical hunting style involving close pursuit of erratically manoeuvring target, and considering how this compares with the proportional navigation guidance law used during similarl level chases by falcons specialised on hunting in open environments.
The research paper is available under the heading, ‘Hawks steer attacks using a guidance system tuned for close pursuit of erratically manoeuvring targets’ available to view in Nature Communications shortly: https://doi.org/10.1038/s41467-019-10454-z. This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme.
Citation: Hawks steer attacks using a guidance system tuned for close pursuit of erratically manoeuvring targets, Caroline H. Brighton & Graham K. Taylor, Nature Communications 10, Article number: 2462 (2019, https://www.nature.com/articles/s41467-019-10454-z
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