Bioinspired Feathered Flapping Wing UAV Design for Operation in Gusty Environment

The flight of unmanned aerial vehicles (UAVs) has numerous associated challenges. Small size is the major reason of their sensitivity towards turbulence restraining them from stable flight. Turbulence alleviation strategies of birds have been explored in recent past in detail to sort out this issue. Besides using primary and secondary feathers, birds also utilize covert feathers deflection to mitigate turbulence. Motivated from covert feathers of birds, this paper presents biologically inspired gust mitigation system (GMS) for a flapping wing UAV (FUAV). GMS consists of electromechanical (EM) covert feathers that sense the incoming gust and mitigate it through deflection of these feathers. A multibody model of gust-mitigating FUAV is developed appending models of the subsystems including rigid body, propulsion system, flapping mechanism, and GMS-installed wings using bond graph modeling approach. FUAV without GMS and FUAV with the proposed GMS integrated in it are simulated in the presence of vertical gust, and results’ comparison proves the efficacy of the proposed design. Furthermore, agreement between experimental results and present results validates the accuracy of the proposed design and developed model.

Flexibility Effects of a Flapping Mechanism Inspired by Insect Musculoskeletal System on Flight Performance

Flying animals such as insects display great flight performances with high stability and maneuverability even under unpredictable disturbances in natural and man-made environments. Unlike man-made mechanical systems like a drone, insects can achieve various flapping motions through their flexible musculoskeletal systems. However, it remains poorly understood whether flexibility affects flight performances or not. Here, we conducted an experimental study on the effects of the flexibility associated with the flapping mechanisms on aerodynamic performance with a flexible flapping mechanism (FFM) inspired by the flexible musculoskeletal system of insects. Based on wing kinematic and force measurements, we found an appropriate combination of the flexible components could improve the aerodynamic efficiency by increasing the wingbeat amplitude. Results of the wind tunnel experiments suggested that, through some passive adjustment of the wing kinematics in concert with the flexible mechanism, the disturbance-induced effects could be suppressed. Therefore, the flight stability under the disturbances is improved. While the FFM with the most rigid spring was least efficient in the static experiments, the model was most robust against the wind within the range of the study. Our results, particularly regarding the trade-off between the efficiency and the robustness, point out the importance of the passive response of the flapping mechanisms, which may provide a functional biomimetic design for the flapping micro air vehicles (MAVs) capable of achieving high efficiency and stability.

A Miniature Flapping Mechanism Using an Origami-Based Spherical Six-Bar Pattern

In this paper, we suggest a novel transmission for the DC motor-based flapping-wing micro aerial vehicles (FWMAVs). Most DC motor-based FWMAVs employ linkage structures, such as a crank-rocker or a crank-slider, which are designed to transmit the motor’s rotating motion to the wing’s flapping motion. These transmitting linkages have shown successful performance; however, they entail the possibility of mechanical wear originating from the friction between relative moving components and require an onerous assembly process owing to several tiny components. To reduce the assembly process and wear problems, we present a geometrically constrained and origami-based spherical six-bar linkage. The origami-based fabrication method reduces the number of the relative moving components by replacing rigid links and pin joints with facets and folding joints, which shortens the assembly process and reduces friction between components. The constrained spherical six-bar linkage enables us to change the motor’s rotating motion to the linear reciprocating motion. Due to the property that every axis passes through a single central point, the motor’s rotating motion is filtered at the spherical linkage and does not transfer to the flapping wing. Only linear motion, therefore, is passed to the flapping wing. To show the feasibility of the idea, a prototype is fabricated and analyzed by measuring the flapping angle, the wing rotation angle and the thrust.

Bionic Flapping Mechanism of the Wings of a Cursorial Dinosaur Robot for Estimating Its Lift and Thrust

We estimated the lift and thrust of the proto-wings of the dinosaur Caudipteryx, a close relative of birds, using both theoretical and experimental approaches. Our experiments utilized a newly reconstructed flapping wing mechanism in accordance to the fossil specimens of Caudipteryx. To ensure that this reconstructed mechanism could adequately simulate the realistic flapping movements, we investigated the relationships among the flapping angle, twisting angle, and stretching angle of the wing mechanism that was driven by a DC motor. We also used two sensors to measure the lift and thrust forces generated by the flapping movements of the reconstructed wing. Our experiment indicated that both the lift and thrust forces produced by the wings were small but increased at higher flapping frequencies. This study not only contributes to current understanding of the origin of avian flight but also usefully informs the ongoing development of bionic flapping robots.

Recent advancements in flapping mechanism and wing design of micro aerial vehicles

Recent studies on understanding of natural flyers have encouraged researchers in development of micro aerial vehicles mimicking birds and insects such as hummingbirds, dragonflies, bats and many more. The vehicles find their applications in reconnaissance and situational awareness in combat field, search and rescue operations, biological and nuclear compromised sites and broadcasting and sports. The focus of this review is to assess recent progress in sub systems of these vehicles including drive mechanisms, actuation mechanisms and wing designs that define the aerodynamics, propulsion, stability, and control of the vehicles. Limited research has been carried out on drive mechanisms capable of producing figure-of-eight wingtip motion contrary to conventional four and five-bar linkage mechanisms along with modified planar and spherical attachments. Motor and piezoelectric actuation mechanisms are being used extensively in these vehicles due to lightweight and power efficiency as compared to non-conventional power sources. Wing shape and rigidity plays a key role in determining the required lift and thrust along with frequency limitations and material constraints. A relatively new field of structural and kinematic optimization for the development of a lightweight flapping vehicle with high endurance capability is also a part of this review. This review has pointed out the research gaps including 3-DoF piezoelectric kinematics, under-actuated mechanisms, structural contact analysis, limited static and dynamic structural analysis, limited fatigue analysis and development of optimization techniques.

A novel piezo-actuated flapping mechanism based on inertia drive

In this article, a novel piezo-actuated flapping mechanism based on inertia drive is proposed and developed. In comparison with the existing flapping mechanisms, the proposed one has a more direct driving form simply via a frictional contact without using any transmission mechanism like crank-rocker or crank-slider, making it easier for miniaturization. In addition, it could principally allow for an arbitrary form of flapping motion with unlimited stroke. The flapping principle and the rationale for an arbitrary form of flapping motion with unlimited stroke are presented. A prototype of the proposed flapping mechanism was constructed and tested. The ability in various modulations of flapping motion, including flapping amplitude, position, asymmetry between downstroke and upstroke flapping speeds, and frequency, is demonstrated.

Development of a novel flapping wing micro aerial vehicle with elliptical wingtip trajectory

This paper describes a novel flapping wing micro air vehicle (FWMAV),which can achieve two active degree of freedom (DOF) movements of flapping and swing, as well as twisting passively. This aircraft has a special “0” figure wingtip motion trajectory with the 140∘ flapping stroke angle. With these characteristics integrated into the simple flapping mechanism, the aerodynamic force is somewhat improved. The model made a balance between the improved aerodynamic performance induced by complicated movements and the increased weight of the extra components in aircraft. In the driven design, Only one micro-motor is employed to drive the wing flapping and swing motion simultaneously forming the prescribed trajectory. The 23 g aircraft could reach the maximum flapping frequency of 11 Hz with the tip-to-tip wingspan of 29 cm.