Acoustic Signature Optimisation for Bioinspired Flapping-Wing Micro Aerial Vehicles

Yi Lun Duh; Krispin C. V. Broers; Sophie F. Armanini

cs.ROOct 27, 2026

Acoustic Signature Optimisation for Bioinspired Flapping-Wing Micro Aerial Vehicles

Authors: Yi Lun Duh, Krispin C. V. Broers, Sophie F. Armanini

Abstract

Flapping-wing micro air vehicles are prized for quiet flight, yet the few existing measurements show engineered wings to be 15-30 dB louder than the animals they imitate. This paper investigates two passive geometric approaches to reduce the acoustic signature of a flapping membrane wing, and applies these to an exemplary wing. A significant sound source in flapping wings is the impulsive click radiated at stroke reversal, when a slack membrane snaps between two curvatures. Our first noise-reduction approach optimises the wing's venation layout, based on an analytical model of the reversal click as a dynamic snap-through of the membrane. The optimised venation pattern was manufactured and resulted in a reduction of up to 8 dB during the reversal snap in experiments. During testing, the venation was found to be sensitive to orientation rather than thickness. Secondly, an additive trailing-edge fringe inspired by hummingbird feathers was shown to further reduce the broadband swoosh by 3-4 dB at no lift cost, matching a cut serration wing without removing lifting area.

Figures & tables

Fig. 1: Wing design framework for acoustically optimising flapping-wing robots.

Fig. 2: Passive-pitch flapping mechanism [ 19 ] featuring the baseline wing design B0.

Panel of Figure 3 — Fig. 3: An overview of the iterative process of the optimisation model.

Fig. 4: Manufactured wing models with the reference wing, the venation pattern set, and the edge-treatment set.

	$\Delta$ dBA	$\Delta L$ (dB)			Lift
Wing	overall	$0^{\circ}$	$90^{\circ}$	$180^{\circ}$	(N)
B0	ref	ref	ref	ref	0.102
M1	$-0.8$	$-2.3$	$-7.8$	$-4.1$	0.112
M1-adverse	$-0.7$	$+0.9$	$-0.2$	$-1.0$	n/a
A negative value is a reduction. $\Delta L$ is the peak reduction in the $80$ – $1000\,\mathrm{Hz}$ band at each microphone position, and lift is the cycle-averaged vertical force.

TABLE I: Experimental Results: Venation Optimisation

Fig. 5: Reversal-averaged snap envelope at the $90^{\circ}$ microphone position for baseline wing B0, venation set M1 and M1-adverse, in normalised amplitude.

	$h$	$\lambda$	$\Delta L$ (dB)			Lift
Wing	(mm)	(mm)	$0^{\circ}$	$90^{\circ}$	$180^{\circ}$	(N)
B0 (plain)	–	–	ref	ref	ref	0.102
F0 (short, fine)	5	7	$-2.1$	$-3.4$	$-3.8$	0.113
F1 (tall, fine)	13	7	$+0.3$	$-1.5$	$-2.0$	0.077
F2 (short, coarse)	5	14	$-2.1$	$-4.8$	$-5.3$	0.100
F3 (tall, coarse)	13	14	$+0.7$	$+1.7$	$-1.2$	0.091

TABLE II: Experimental Results: Trailing-Edge Fringe Patterns

Fig. 6: Reversal-averaged swoosh envelope at the $90^{\circ}$ microphone position for the baseline wing B0 and the fringe pattern wing F2 in normalised amplitude.

Aerial Robotics

Aerial robotics studies the design, perception, control, and coordination of flying robots for navigation, inspection, transport, and physical interaction.

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Jun 20, 2026J/K move · Enter open · S save

A Multimodal Tiltwing Framework for Bioinspired Aerial Robots

Krispin C. V. Broers, Sophie F. Armanini

Department of Aeronautics, Imperial College London, London, SW7 2AZ, UK

Robotic Control Aerial Robotics

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Tailless flapping-wing micro-aerial vehicles (FWMAVs) mimic the impressive flight performance of hummingbirds, utilising unsteady aerodynamic effects. However, existing designs are still limited and purpose-built with a restricted flight envelope and poor endurance. We therefore propose an adaptable tiltwing framework enabling bioinspired aerial robots to switch between hovering flight, high-speed directional flight, and energy-efficient gliding flight. The proposed framework utilises thrust vectoring with a wide actuation range via two fully independent propulsion units, each flapping a single wing, for effective control and enhanced manoeuvrability. For this, we developed a hybrid Scotch-yoke-based flapping mechanism that ensures a symmetric motion profile with a modular design guaranteeing an arbitrarily wide flapping angle to exploit the lift-enhancing clap-and-fling effect. Additionally, we implemented a passive wing-rotation mechanism, which, in combination with our dual-wing thrust-vectoring approach, allows unprecedented wing-design freedom, unlocking potential for precise optimisation. A contactless leading-edge tracking sensor provides accurate feedback on the wing's orientation and, in the gliding mode, enables dihedral-angle control, augmenting the active wing-pitch control. Extensive testing of a propulsion unit was conducted with a six-axis force/torque sensor, demonstrating the flapping mechanism's performance while optimising transmission efficiency and the passive wing-pitch mechanism. At full throttle, the average lift force generated by a single wing, flapping with a 188° amplitude, was 21.1 gf for a small 3.1 g 1S BLDC motor. Additional tests covering the full range of the wide-angle tilting capability showed an effective thrust-vectoring control architecture with a linear and symmetric response curve of the moments generated.

Abstract

Aerial Robotics

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