Wing rapid responses and aerodynamics of fruit flies during headwind gust perturbations

Fly Me to the Micron: Microtechnologies for Drosophila Research

Multicellular model organisms, such as Drosophila melanogaster (fruit fly), are frequently used in a myriad of biological research studies due to their biological significance and global standardization. However, traditional tools used in these studies generally require manual handling, subjective phenotyping, and bulk treatment of the organisms, resulting in laborious experimental protocols with limited accuracy. Advancements in microtechnology over the course of the last two decades have allowed researchers to develop automated, high-throughput, and multifunctional experimental tools that enable novel experimental paradigms that would not be possible otherwise. We discuss recent advances in microtechnological systems developed for small model organisms using D. melanogaster as an example. We critically analyze the state of the field by comparing the systems produced for different applications. Additionally, we suggest design guidelines, operational tips, and new research directions based on the technical and knowledge gaps in the literature. This review aims to foster interdisciplinary work by helping engineers to familiarize themselves with model organisms while presenting the most recent advances in microengineering strategies to biologists.

Wing kinematics measurement and aerodynamics of hovering droneflies with wing damage

In this study, we performed successive unilateral and bilateral wing shearing to simulate wing damage in droneflies (Eristalis tenax) and measured the wing kinematics using high-speed photography technology. Two different shearing types were considered in the artificial wing damage. The aerodynamic force and power consumption were obtained by numerical method. Our major findings are the following. Different shearing methods have little influence on the kinematics, forces and energy consumption of insects. Following wing damage, among the potential strategies to adjust the three Euler angles of the wing, adjusting stroke angle (φ) in isolation, or combing the adjustment of stroke angle (φ) with pitch angle (ψ), contributed most to the change in vertical force. The balance of horizontal thrust can be restored by the adjustment of deviation angle (θ) under the condition of unilateral wing damage. Considering zero elastic energy storage, the mass-specific power (P₁) increases significantly following wing damage. However, the increase in mass-specific power with 100% elastic energy storage (P₂) is very small. The extra cost of the unilateral wing damage is that the energy consumption of the damaged wing and intact wing is highly asymmetrical when zero elastic energy storage is considered. The insects may alleviate the problems of increasing power consumption and asymmetric power distribution by storage and reuse of the negative inertial work of the wing.

Embodied airflow sensing for improved in-gust flight of flapping wing MAVs

Flapping wing micro aerial vehicles (FWMAVs) are known for their flight agility and maneuverability. These bio-inspired and lightweight flying robots still present limitations in their ability to fly in direct wind and gusts, as their stability is severely compromised in contrast with their biological counterparts. To this end, this work aims at making in-gust flight of flapping wing drones possible using an embodied airflow sensing approach combined with an adaptive control framework at the velocity and position control loops. At first, an extensive experimental campaign is conducted on a real FWMAV to generate a reliable and accurate model of the in-gust flight dynamics, which informs the design of the adaptive position and velocity controllers. With an extended experimental validation, this embodied airflow-sensing approach integrated with the adaptive controller reduces the root-mean-square errors along the wind direction by 25.15% when the drone is subject to frontal wind gusts of alternating speeds up to 2.4 m/s, compared to the case with a standard cascaded PID controller. The proposed sensing and control framework improve flight performance reliably and serve as the basis of future progress in the field of in-gust flight of lightweight FWMAVs.

Flying Into the Wind: Insects and Bio-Inspired Micro-Air-Vehicles With a Wing-Stroke Dihedral Steer Passively Into Wind-Gusts

Natural fliers utilize passive and active flight control strategies to cope with windy conditions. This capability makes them incredibly agile and resistant to wind gusts. Here, we study how insects achieve this, by combining Computational Fluid Dynamics (CFD) analyses of flying fruit flies with freely-flying robotic experiments. The CFD analysis shows that flying flies are partly passively stable in side-wind conditions due to their dorsal-ventral wing-beat asymmetry defined as wing-stroke dihedral. Our robotic experiments confirm that this mechanism also stabilizes free-moving flapping robots with similar asymmetric dihedral wing-beats. This shows that both animals and robots with asymmetric wing-beats are dynamically stable in sideways wind gusts. Based on these results, we developed an improved model for the aerodynamic yaw and roll torques caused by the coupling between lateral motion and the stroke dihedral. The yaw coupling passively steers an asymmetric flapping flyer into the direction of a sideways wind gust; in contrast, roll torques are only stabilizing at high air gust velocities, due to non-linear coupling effects. The combined CFD simulations, robot experiments, and stability modeling help explain why the majority of flying insects exhibit wing-beats with positive stroke dihedral and can be used to develop more stable and robust flapping-wing Micro-Air-Vehicles.

Effect of passive wing pitching on flight control in a hovering model insect and flapping-wing micro air vehicle

Passive wing pitching is a hypothesis in insect flight, and it is used widely by most flapping-wing micro air vehicles (FWMAVs). This study analyses the flight control of hovering model fruit fly and FWMAV with passive pitching wings. The longitudinal and lateral control derivatives are obtained by numerical simulation of the fluid dynamic equations coupled with the torsional spring passive pitching system. In contrast to active pitching wings, some of the control derivatives are remarkably changed by passive pitching wings, such asZ_Φ(vertical force produced by unit stroke amplitude),Z_f(vertical force produced by unit flapping frequency), andMψ0(pitching moment produced by unit rest angle). For example, increasing flapping frequency does not lead to an evident increase in lift and may even have a reverse effect. Therefore, the flight control of FWMAV with passive pitching wings should be treated with caution. For wings pitching passively with a torsional spring at the root, the differential change of the angle of attack in the downstroke and upstroke (α_dandα_u) could be achieved by modulation of the rest angle alone; however, the equal change inα_dandα_umay require an otherwise manipulation of the elastic coefficient. Results in this study provide guidelines for the design of FWMAVs in evaluating the effects of different control inputs correctly and formulating a cost-effective control scheme.