An overview of experiments on the dynamic sensitivity of MAVs to turbulence

Watkins, Simon; Thompson, Mark; Shortis, Mark R.; Segal, Reuven; Abdulrahim, Mujahid; Sheridan, John

doi:10.1017/s0001924000003973

Cited by 18 publications

(10 citation statements)

References 9 publications

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“…In the highly turbulent flow environment generated here, the hummingbirds' heads were likely to be subjected to translational and rotational disturbances induced by both the unsteady wind and by disturbances propagated from the body to the head, through the neck. Given these imposed perturbations, the hummingbirds maintained remarkably stable head position and orientation, displaying <1.5 mm fluctuations in head position while flying in relative turbulence intensities that would ground most current micro air vehicles (Abdulrahim et al, 2010;Watkins et al, 2009; supplementary material Movies 1 and 2). Accelerations of the head were nearly two orders of magnitude lower than those present in the oncoming flow (see Fig.…”

Section: Discussion Effects Of Unsteady Flow On Flight Stabilitymentioning

confidence: 99%

Hummingbird flight stability and control in freestream turbulent winds

Ravi

Crall

McNeilly

et al. 2015

Journal of Experimental Biology

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Airflow conditions close to the Earth's surface are often complex, posing challenges to flight stability and control for volant taxa. Relatively little is known about how well flying animals can contend with complex, adverse air flows, or about the flight control mechanisms used by animals to mitigate wind disturbances. Several recent studies have examined flight in the unsteady von Kaŕmań vortex streets that form behind cylinders, generating flow disturbances that are predictable in space and time; these structures are relatively rare in nature, because they occur only the immediate, downstream vicinity of an object. In contrast, freestream turbulence is characterized by rapid, unpredictable flow disturbances across a wide range of spatial and temporal scales, and is nearly ubiquitous in natural habitats. Hummingbirds are ideal organisms for studying the influence of freestream turbulence on flight, as they forage in a variety of aerial conditions and are powerful flyers. We filmed ruby-throated hummingbirds (Archilochus colubris) maintaining position at a feeder in laminar and strongly turbulent (intensity ∼15%) airflow environments within a wind tunnel and compared their mean kinematics of the head, body, tail and wing, as well as variability in these parameters. Hummingbirds exhibited remarkably stable head position and orientation in both smooth and turbulent flow while maintaining position at the feeder. However, the hummingbird's body was less stable in turbulent flow and appeared to be most sensitive to disturbances along the mediolateral axis, displaying large lateral accelerations, translations and rolling motions during flight. The hummingbirds mitigated these disturbances by increasing mean wing stroke amplitude and stroke plane angle, and by varying these parameters asymmetrically between the wings and from one stroke to the next. They also actively varied the orientation and fan angle of the tail, maintaining a larger mean fan angle when flying in turbulent flow; this may improve their passive stability, but probably incurs an energetic cost as a result of increased drag. Overall, we observed many of the same kinematic changes noted previously for hummingbirds flying in a von Kaŕmań vortex street, but we also observed kinematic changes associated with high force production, similar to those seen during load-lifting or high-speed flight. These findings suggest that flight may be particularly costly in fully mixed, freestream turbulence, which is the flow condition that hummingbirds are likely to encounter most frequently in natural habitats.

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Section: Discussion Effects Of Unsteady Flow On Flight Stabilitymentioning

confidence: 99%

Hummingbird flight stability and control in freestream turbulent winds

Ravi

Crall

McNeilly

et al. 2015

Journal of Experimental Biology

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“…Gamble et al 22 conducted an experimental investigation of the propeller slipstream on a flexible wing FMAV that had a 24 inch wing span. Watkins et al 23 wrote an article that gave an overview of experiments on the dynamic sensitivity of MAV to turbulence. Sadeghi et al 24 investigated the characteristics of the unsteady flow field in the downstream wake of a pitch-oscillating Eppler-361 airfoil.…”

Section: Fixed-wing Micro Air Vehiclesmentioning

confidence: 99%

A bibliometric review of progress in micro air vehicle research

Ward

Fearday

Salami

et al. 2017

International Journal of Micro Air Vehicles

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Micro air vehicle research has exponentially expanded since the first articles began to be published in the late 1990s. This article presents a comprehensive bibliometric review of journal articles published on micro air vehicle research from 1998 until 2015. The articles are classified into three types of micro air vehicle: fixed-wing, rotary-wing, and flapping-wing (biomimetic). These types are based upon their primary means of generating lift and propulsive thrust. The specific type of research in these articles is also examined, divided into subcategories of: aerodynamics; guidance, navigation, and control; propulsion; structures and materials; and system design. Numerous bibliometric indicators are presented and analyzed to understand how micro air vehicle research is expanding, which authoring organizations are leading the research, which external sponsoring organizations are providing funding, and the challenges that remain for future researchers. The analysis shows that the majority of the research articles are being written by organizations from the US, China, UK, France, and South Korea. Although biomimetic micro air vehicles are currently the most popular type of micro air vehicle, in recent years the growing popularity of rotary-wing micro air vehicles (especially as a guidance, navigation, and control test platform) has caused it to rival biomimetic micro air vehicles in popularity.

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“…shows the set‐up of coded targets in the test section of the 12 m by 4 m wind tunnel at Monash University in Melbourne, Australia. These targets provided resection points for an Agent USB video camera used to track a powered model aircraft in laminar and turbulent airflows (Watkins et al., ). The video camera, recording in 800 by 600 pixel resolution mode to respect bandwidth limitations, was operated with a red filter to isolate red LEDs on the wing tips of the model aircraft.…”

Section: Application Examplesmentioning

confidence: 99%

A practical target recognition system for close range photogrammetry

Shortis

Seager²

2014

The Photogrammetric Record

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This paper presents details of a coded target system that employs polar coordinate transformation and segment matching to automatically recognise and identify targets in digital images. The code system is based on a square surrounding the central circular target and is described at a level of detail that would allow the system to be readily duplicated. Pre-detection processes, developed to improve the success rate under unfavourable conditions, and the tests conducted to validate a correct target match, are described. Finally, the paper includes some examples of the use of the coded targets, drawn from a variety of calibration and measurement applications.

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An overview of experiments on the dynamic sensitivity of MAVs to turbulence

Cited by 18 publications

References 9 publications

Hummingbird flight stability and control in freestream turbulent winds

Hummingbird flight stability and control in freestream turbulent winds

A bibliometric review of progress in micro air vehicle research

A practical target recognition system for close range photogrammetry

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