Bio-inspired flapping wing robots with foldable or deformable wings: a review

Abstract

Traditional flapping-wing robots (FWRs) obtain lift and thrust by relying on the passive deformation of their wings which cannot actively fold or deform. In contrast, flying creatures such as birds, bats, and insects can maneuver agilely through active folding or deforming their wings. Researchers have developed many bio-inspired foldable or deformable wings (FDWs) imitating the wings of flying creatures. The foldable wings refer to the wings like the creatures’ wings that can fold in an orderly manner close to their bodies. Such wings have scattered feathers or distinct creases that can be stacked and folded to reduce the body envelope, which in nature is beneficial for these animals to prevent wing damage and ensure agility in crossing bushes. The deformable wings refer to the active deformation of the wings using active driving mechanisms and the passive deformation under the aerodynamic force, which functionally imitates the excellent hydrodynamic performance of the deformable body and wings of the creatures. However, the shape and external profile changes of deformable wings tend to be much smaller than that of folding wings. FDWs enable the FWRs to improve flight degree of flexibility, maneuverability, and efficiency and reduce flight energy consumption. However, FDWs still need to be studied, and a comprehensive review of the state-of-the-art progress of FDWs in FWR design is lacking. This paper analyzes the wing folding and deformation mechanisms of the creatures and reviews the latest progress of FWRs with FDWs. Furthermore, we summarize the current limitations and propose future directions in FDW design, which could help researchers to develop better FWRs for safe maneuvering in obstacle-dense environments.

A numerical study on the aerodynamic effects of dynamic twisting on forward flight flapping wings

“…To investigate the validity of the aforementioned findings across various advanced ratios (J), we conducted a comprehensive study that incorporated a wider range of forward velocity. Based on previous measurements of hummingbird flight kinematics [1], it has been deduced that minimal modifications occur in wingbeat frequency and wingbeat amplitude as freestream velocities increase. Instead, hummingbirds achieve faster forward flight primarily by making adjustments to the stroke plane angle and pitching kinematics of their wings.…”

“…The propulsion efficiency of flapping wing has consistently provided inspiration for researchers. The ability to replicate the intricate motion observed in birds and insects have significant implications for the applications of micro-air vehicles (MAVs) [1]. In flapping-wing MAVs, the wings play a dual role in generating both lift and thrust during fast forward flight.…”

The Functions of Phasic Wing-Tip Folding on Flapping-Wing Aerodynamics

“…Micro-air-vehicles predominantly employ flapping-wing flight methods, which imitate the flight principle of insects. The flapping-wing flight mode offers superior energy efficiency when the wings are small, a crucial advantage for micro-air-vehicles where energy consumption is a key factor [ 5 ].…”

The Aerodynamic Effect of Biomimetic Pigeon Feathered Wing on a 1-DoF Flapping Mechanism

“…This adaptability enables birds to employ the most efficient modes of motion and flight strategies to accommodate various flight conditions and purposes [3,4]. Previous studies have predominantly relied on methods such as biological observation [5,6], numerical simulations [7,8], and scale-model wind tunnel experiments [9][10][11]. While birds may not match the agility of smaller insects, their larger size grants them access to higher flight altitudes, greater speeds, increased payload capacity, and extended ranges.…”