Flapping Wing Nano Air Vehicles Research Articles

Computational evaluation of flight performance of flapping-wing nano air vehicles using hierarchical coupling of nonlinear dynamic and fluid-structure interaction analyses

This study endeavours to introduce an inventive hierarchical coupling methodology for evaluating the flight capabilities of polymer micromachined flapping-wing nano air vehicles (FWNAVs) using advanced computational tools. Furthermore, our objective is to provide a practical demonstration of FWNAVs in both tethered and airborne scenarios. These dual objectives represent the distinctive and pioneering aspects of this research. Such FWNAVs, which are insect-inspired robots, have a 2.5-dimensional structure. An FWNAV comprises a micro piezoelectric drive system and a pair of micro thin flexible wings. The drive system includes a micro transmission and a piezoelectric bimorph actuator. The flight performance of the designed FWNAV is evaluated using a hierarchical coupling approach, where the whole system is decomposed into a micro wing and a micro piezoelectric drive system. The coupling between these parts is modelled as one-way coupling and that between the micro wings and the surrounding air is modelled as strong coupling. In the one-way coupling analysis, nonlinear structural dynamic analysis is conducted for the micro piezoelectric drive system, where the dynamic response is transmitted to the micro wings via the Dirichlet boundary condition. In the strong coupling analysis, strongly coupled fluid-structure interaction analysis is conducted for the micro wings and the surrounding air to consider their strong coupling. The optimisation of flight performance is conducted using fluid-structure interaction analysis to achieve sufficient lift force to support the weight of an FWNAV. The design of a tethered and flyable FWNAV with a size of 10 mm or smaller is demonstrated. This FWNAV can be easily fabricated using polymer micromachining.

Computational Approach for the Fluid-Structure Interaction Design of Insect-Inspired Micro Flapping Wings

A flight device for insect-inspired flapping wing nano air vehicles (FWNAVs), which consists of the micro wings, the actuator, and the transmission, can use the fluid-structure interaction (FSI) to create the characteristic motions of the flapping wings. This design will be essential for further miniaturization of FWNAVs, since it will reduce the mechanical and electrical complexities of the flight device. Computational approaches will be necessary for this biomimetic concept because of the complexity of the FSI. Hence, in this study, a computational approach for the FSI design of insect-inspired micro flapping wings is proposed. This approach consists of a direct numerical modeling of the strongly coupled FSI, the dynamic similarity framework, and the design window (DW) search. The present numerical examples demonstrated that the dynamic similarity framework works well to make different two FSI systems with the strong coupling dynamically similar to each other, and this framework works as the guideline for the systematic investigation of the effect of characteristic parameters on the FSI system. Finally, an insect-inspired micro flapping wing with the 2.5-dimensional structure was designed using the proposed approach such that it can create the lift sufficient to support the weight of small insects. The existing area of satisfactory design solutions or the DW increases the fabricability of this wing using micromachining techniques based on the photolithography in the micro-electro-mechanical systems (MEMS) technology. Hence, the proposed approach will contribute to the further miniaturization of FWNAVs.

One-wing polymer micromachined transmission for insect-inspired flapping wing nano air vehicles

This paper presents a feasibility step in the development of an insect-inspired flapping wing nano air vehicle using advanced engineering technologies such as microelectromechanical systems (MEMS) technologies. To develop an insect-inspired flapping wing nano air vehicle, a one-wing polymer micromachined transmission is proposed in this paper. The novelty of this study includes (1) the use of the geometrically nonlinear bending deformation of a set of two parallel elastic hinges as the basis for the transmission mechanism, which produces a large rotational displacement from a small translational displacement, and (2) a complete 2.5-dimensional structure that can be fabricated using standard microfabrication techniques, including etching, photolithography, deposition, and curing, without any post-assembly. This design is also an improved version of our previous design, a two-wing polymer micromachined transmission. The transmission proposed here has a great advantage over other types of transmission mechanisms, including its low energy loss because no post-assembly is required (reduced friction loss); its low total weight; its capacity to be further miniaturized without difficulty; and its performance, i.e., ability to produce the necessary stroke angle of approximately 30° without resonance assistance.

Aerodynamic Model Updating Using Wind-Tunnel Setup for Hummingbirdlike Flapping Wing Nanorobot

The complex wing motion of insects and small birds leads to high lift production in nature. Specific lift-enhancing mechanisms arise from the combination of a horizontal stroke motion and a secondary wing pitching motion. Research around flapping wing nano air vehicles (FWNAVs) copies this wing motion to fly small drones, in an effort to benefit from the same mechanisms. A flapping wing aerodynamic model can predict the force production of the FWNAV and helps to understand the influence of the wing kinematics thereon. This work starts from a quasi-steady model expression for the aerodynamics and proposes a wind-tunnel procedure to identify the force coefficients in the model empirically. The procedure is based on a test case performed by the AVT-202 research team that combines wing translation and wing rotation, imitating the aerodynamic condition of the flapping wing in a simplified setup. Comparison of measurements and model simulations demonstrates that the procedure can be used to update the model parameters for our specific FWNAV configuration, leading to an empirical relation for the force coefficients. Simulations with the updated model using the empirical relations show good agreement with measured force production for a wide range of input variables.

Insights into Sensitivity of Wing Shape and Kinematic Parameters Relative to Aerodynamic Performance of Flapping Wing Nano Air Vehicles

In this work, seven wings inspired from insects’ wings, including those inspired by the bumblebee, cicada, cranefly, fruitfly, hawkmoth, honeybee, and twisted parasite, are patterned and analyzed in FlapSim software in forward and hovering flight modes for two scenarios, namely, similar wingspan (20 cm) and wing surface (0.005 m2). Considering their similar kinematics, the time histories of the aerodynamic forces of lift, thrust, and required mechanical power of the inspired wings are calculated, shown, and compared for both scenarios. The results obtained from FlapSim show that wing shape strongly impacts the performance and aerodynamic characteristics of the chosen seven wings. To study the effects of different geometrical and physical factors including flapping frequency, elevation amplitude, pronation amplitude, stroke-plane angle, flight speed, wing material, and wingspan, several analyses are carried out on the honeybee-inspired shape, which had a 20 cm wingspan. This study can be used to evaluate the efficiency of different bio-inspired wing shapes and may provide a guideline for comparing the performance of flapping wing nano air vehicles with forward flight and hovering capabilities.

Sizing process, aerodynamic analysis, and experimental assessment of a biplane flapping wing nano air vehicle

The design, manufacturing, experimentation, performance analysis, and flight test for a biplane flapping wing nano air vehicle, capable of both forward and hovering flight are presented. To design this nano air vehicle, a comprehensive sizing method based on theoretical and statistical analyses is proposed and experimentally verified. Then, aerodynamic analyses based on quasi-steady and strip theory methods are conducted to select the optimum values for the kinematics. To evaluate the proposed conceptual design obtained from the sizing methodology and aerodynamic analyses, an experimental setup deploying strain gauges mounted on a thin aluminum plate is implemented. This setup is also deployed to identify the wing configuration resulting in the highest thrust generation and lowest power consumption. The experimental results are found in a good agreement with the aerodynamic simulations. To ensure the stability of the air vehicle and a smooth transition between the different flying modes, magnetic coils are mounted on the tail to actuate the elevator and rudder. A flight test was successfully performed indoor to demonstrate the flying capabilities of the air vehicle and the camera showed a clear visual inspection of the area. It showed stable behavior especially during the transition from forward flight to hovering and superior flight endurance in comparison to similar air vehicles reported in the literature. The proposed and applied design methodologies along with the manufacturing process are expected to provide useful guidelines to design and manufacture different types of flapping wings to support various applications.

Investigation on the planform and kinematic optimization of bio-inspired nano air vehicles for hovering applications

Wing shape and kinematics of flapping wing nano air vehicles are two important factors in their design process. These factors require an optimal design in terms of decreasing the needed aerodynamic power. Since, insects are regarded as the best natural flier in hovering flight, seven of their wings are considered in order to determine the best wing shape for hovering applications. Because of the difference in the original bio-inspired shape of these wings, two scenarios are studied, namely, considering the same wingspan and same wing surface. Using the quasi-steady approximation to model the aerodynamic loads and a basic gradient approach to optimize the kinematics of the wing, the optimum Euler angles, required aerodynamic power, and hence the best wing shape for each scenario are analytically determined. The results show that the wing shape and surface strongly impact the aerodynamic characteristics and performances of the chosen wing shapes. It is demonstrated that the twisted parasite wing shape is a good candidate to minimize the required aerodynamic power during hovering. The strategy used in this analysis can be used to evaluate the performance of any realistic wing shape design and could provide a guideline for selecting the best wing shape and kinematics for flapping wing nano air vehicles with hovering capabilities.

Wing shape and dynamic twist design of bio-inspired nano air vehicles for forward flight purposes

The wing shape and kinematics of flapping wing nano air vehicles play a crucial role in the effectiveness of the system. Optimizing these design parameters allows for greater endurance during flight due to a reduction in the needed aerodynamic power. In this study, seven insects' wings are considered in order to investigate which wing shape requires less amount of aerodynamic power for forward flight missions. A strip theory model is employed and verified for two types of birds, namely, Jack Daw, and Mew Gull. Then, this aerodynamic theory is utilized to model and optimize the kinematics of the seven wings with a particular investigation on the impacts of the dynamic twist on the performance of bio-inspired nano air vehicles. Each wing is divided into strips that are individually analyzed and integrated over the full wingspan to determine the needed aerodynamic power and propulsive efficiency. The use of this modified strip theory is beneficial because it includes the unsteady aerodynamic effects and the possible change in the wings' dimensions. A parametric study is then carried out to determine the optimum wing shape and associated dynamic twist of the flapping wing nano air vehicle when considering two scenarios. In the first scenario, the wingspan for all considered seven wing shapes is considered the same. As for the second scenario, the seven wing shapes are considered with same wing surface. The results show that for same wingspan and wing surface, the bio-inspired honeybee and bumblebee wing shapes have the optimum performances, respectively. The performed analysis gives guidelines on the optimum design of flapping wing nano air vehicles for forward flight applications.