Abstract
Recently, a novel concept of flapping Micro-Air-Vehicles (FMAVs) with four wings has been proposed, which potentially utilizes the clap-and-fling effect for lift enhancement and agile maneuvers through an adjustment of wing kinematics. However, the application of the clap-and-fling effect in the four-winged FMAVs is underexplored and the dynamic stability is still unclear. In this paper, aerodynamics and flight dynamic stability of the four-winged FMAVs are studied experimentally and numerically. Results show that the clap-and-fling effect is observed when the flapping frequency is above 18 Hz. Due to the clap-and-fling effect, the lift generation and aerodynamic efficiency are both improved, which is mainly attributed to the fling phase. Further studies show that the clap-and-fling effect becomes weaker as the wing root spacing increases and is almost absent at a wing root spacing of 1.73 chord length. In addition, a wing with an aspect ratio of 3 can increase both lift generation and efficiency due to the clap-and-fling effect. Finally, according to the dynamic stability analysis of the four-winged FMAV, the divergence speed of the lateral oscillation mode is about 4 times faster than that of the longitudinal oscillation mode. Our results can provide guidance on the design and control of four-winged FMAVs.
Highlights
With the rapid development of microelectronics and microfabrication technology, the concept of Micro-Air-Vehicle (MAV) [1] has been proposed by the Defense Advanced Research Projects Agency (DARPA) in the 1990s
3.1 Aerodynamic performance of a typical micro four-wing flapping Micro-Air-Vehicles (FMAVs) Averaged lift of a typical micro four-winged FMAV model was firstly measured to verify the effect of the clap-and-fling effect on lift production
Once the flapping frequency is higher than 18 Hz, lift produced by wing with clap-and-fling effect motion becomes larger than that without the motion and the lift difference caused by clap-and-fling effect almost increases linearly with wing flapping frequency
Summary
With the rapid development of microelectronics and microfabrication technology, the concept of Micro-Air-Vehicle (MAV) [1] has been proposed by the Defense Advanced Research Projects Agency (DARPA) in the 1990s. In the last two decades, the unsteady high-lift mechanisms and flight mechanics of natural insects have been widely studied and their feasibility applied into FMAV design has been proved [3,4,5]. With the theories how insects fly in mind, scientists turned their focus into how to fully apply those flying principles to a man-made FMAV and conducted systematical researches on aerodynamic, structure, power and control problems. Extensive experimental and numerical studies have been conducted on the effects of wing geometrical [14,15,16] (including wing aspect ratio, area, span et al.) and on both lift and power consumption. After flying test of both vertical take-off and hovering flight, the dynamic stability of those bionic FMAVs has been further studied to guide flight control system design so as to achieve maneuvering flight
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