Clap-and-fling mechanism in a hovering insect-like two-winged flapping-wing micro air vehicle

Abstract

This study used numerical and experimental approaches to investigate the role played by the clap-and-fling mechanism in enhancing force generation in hovering insect-like two-winged flapping-wing micro air vehicle (FW-MAV). The flapping mechanism was designed to symmetrically flap wings at a high flapping amplitude of approximately 192°. The clap-and-fling mechanisms were thereby implemented at both dorsal and ventral stroke reversals. A computational fluid dynamic (CFD) model was constructed based on three-dimensional wing kinematics to estimate the force generation, which was validated by the measured forces using a 6-axis load cell. The computed forces proved that the CFD model provided reasonable estimation with differences less than 8%, when compared with the measured forces. The measurement indicated that the clap and flings at both the stroke reversals augmented the average vertical force by 16.2% when compared with the force without the clap-and-fling effect. In the CFD simulation, the clap and flings enhanced the vertical force by 11.5% and horizontal drag force by 18.4%. The observations indicated that both the fling and the clap contributed to the augmented vertical force by 62.6% and 37.4%, respectively, and to the augmented horizontal drag force by 71.7% and 28.3%, respectively. The flow structures suggested that a strong downwash was expelled from the opening gap between the trailing edges during the fling as well as the clap at each stroke reversal. In addition to the fling phases, the influx of air into the low-pressure region between the wings from the leading edges also significantly contributed to augmentation of the vertical force. The study conducted for high Reynolds numbers also confirmed that the effect of the clap and fling was insignificant when the minimum distance between the two wings exceeded 1.2c (c = wing chord). Thus, the clap and flings were successfully implemented in the FW-MAV, and there was a significant improvement in the vertical force.

Towards Bio-Inspiration, Development, and Manufacturing of a Flapping-Wing Micro Air Vehicle

“…There is a large variety of actuation mechanisms used in the manufacturing of drones [10][11][12][13][14][15][16][17][18][19]. When selecting these mechanisms, many crucial factors must be considered and compared to select the appropriate actuator for the desired drone design.…”

KUBeetle-S: An insect-like, tailless, hover-capable robot that can fly with a low-torque control mechanism

“…16 Flapping amplitude is approximately 190 allowing the presence of clap-and-fling effect for vertical force augmentation. 27 Effect of vein structures on force generation and power requirement was also investigated previously. 28…”

Aerodynamic mechanisms in bio‐inspired micro air vehicles: a review in the light of novel compound layouts

“…A combination of four‐bar linkage and pulley‐string mechanisms was applied as the lightweight flapping mechanism that can achieve a flapping amplitude of about 190°. The enlarged flapping amplitude provided a chance for the wings to clap together at dorsal and ventral stroke reversals and thus the clap‐and‐flings mechanism was implemented to enhance the lift generation [32]. A gearbox with a reduction ratio of 20.6:1 was used and the mechanism was driven by a coreless DC motor.…”