From Studying Real Hummingbirds to Designing Hummingbird-Like Robots—A Literature Review <s> A. MORPHOLOGY INTRODUCTION OF INSECTS AND FLYER ROBOTICS INSPIRED BY THE INSECTS <s> 1. On the assumption that steady-state aerodynamics applies, simple analytical expressions are derived for the average lift coefficient, Reynolds number, the aerodynamic power, the moment of inertia of the wing mass and the dynamic efficiency in animals which perform normal hovering with horizontally beating wings. 2. The majority of hovering animals, including large lamellicorn beetles and sphingid moths, depend mainly on normal aerofoil action. However, in some groups with wing loading less than 10 N m -2 (1 kgf m -2 ), non-steady aerodynamics must play a major role, namely in very small insects at low Reynolds number, in true hover-flies (Syrphinae), in large dragonflies (Odonata) and in many butterflies (Lepidoptera Rhopalocera). 3. The specific aerodynamic power ranges between 1.3 and 4.7 WN -1 (11-40 cal h -1 gf -1 ) but power output does not vary systematically with size, inter alia because the lift/drag ratio deteriorates at low Reynolds number. 4. Comparisons between metabolic rate, aerodynamic power and dynamic efficiency show that the majority of insects require and depend upon an effective elastic system in the thorax which counteracts the bending moments caused by wing inertia. 5. The free flight of a very small chalcid wasp Encarsia formosa has been analysed by means of slow-motion films. At this low Reynolds number (10-20), the high lift co-efficient of 2 or 3 is not possible with steady-state aerodynamics and the wasp must depend almost entirely on non-steady flow patterns. 6. The wings of Encarsia are moved almost horizontally during hovering, the body being vertical, and there are three unusual phases in the wing stroke: the clap , the fling and the flip . In the clap the wings are brought together at the top of the morphological upstroke. In the fling, which is a pronation at the beginning of the morphological downstroke, the opposed wings are flung open like a book, hinging about their posterior margins. In the flip, which is a supination at the beginning of the morphological upstroke, the wings are rapidly twisted through about 180°. 7. The fling is a hitherto undescribed mechanism for creating lift and for setting up the appropriate circulation over the wing in anticipation of the downstroke. In the case of Encarsia the calculated and observed wing velocities at which lift equals body weight are in agreement, and lift is produced almost instantaneously from the beginning of the downstroke and without any Wagner effect. The fling mechanism seems to be involved in the normal flight of butterflies and possibly of Drosophila and other small insects. Dimensional and other considerations show that it could be a useful mechanism in birds and bats during take-off and in emergencies. 8. The flip is also believed to be a means of setting up an appropriate circulation around the wing, which has hitherto escaped attention; but its operation is less well understood. It is not confined to Encarsia but operates in other insects, not only at the beginning of the upstroke (supination) but also at the beginning of the downstroke where a flip (pronation) replaces the clap and fling of Encarsia . A study of freely flying hover-flies strongly indicates that the Syrphinae (and Odonata) depend almost entirely upon the flip mechanism when hovering. In the case of these insects a transient circulation is presumed to be set up before the translation of the wing through the air, by the rapid pronation (or supination) which affects the stiff anterior margin before the soft posterior portions of the wing. In the flip mechanism vortices of opposite sense must be shed, and a Wagner effect must be present. 9. In some hovering insects the wing twistings occur so rapidly that the speed of propagation of the elastic torsional wave from base to tip plays a significant role and appears to introduce beneficial effects. 10. Non-steady periods, particularly flip effects, are present in all flapping animals and they will modify and become superimposed upon the steady-state pattern as described by the mathematical model presented here. However, the accumulated evidence indicates that the majority of hovering animals conform reasonably well with that model. 11. Many new types of analysis are indicated in the text and are now open for future theoretical and experimental research. <s> BIB001 </s> From Studying Real Hummingbirds to Designing Hummingbird-Like Robots—A Literature Review <s> A. MORPHOLOGY INTRODUCTION OF INSECTS AND FLYER ROBOTICS INSPIRED BY THE INSECTS <s> Morphological parameters are presented for a variety of insects that have been filmed in free flight. The nature of the parameters is such that they can be divided into two distinct groups: gross parameters and shape parameters. The gross parameters provide a very crude, first-order description of the morphology of a flying animal: its mass, body length, wing length, wing area and wing mass. Another gross parameter of the wings is their virtual mass, or added mass, which is the mass of air accelerated and decelerated together with the wing at either end of the wingbeat. The wing motion during these accelerations is almost perpendicular to the wing surface, and the virtual mass is approximately given by the mass of air contained in an imaginary cylinder around the wing with the chord as its diameter. The virtual mass ranges from 0.3 to 1.3 times the actual wing mass, indicating that the total mass accelerated by the flight muscles can be more than twice the wing mass itself. Over the limited size range of insects in this study, the interspecific variation of non-dimensional forms of the gross parameters is much greater than any systematic allometric variation, and no interspecific correlations can be found. The new shape parameters provide quite a surprise, however: intraspecific coefficients of variation are very low, often only 1%, and interspecific allometric relations are extremely strong. Mechanical aspects of flight depend not only on the magnitude of gross morphological quantities, but also on their distributions. Non-dimensional radii are derived from the non-dimensional moments of the distributions; for example, the first radius of wing mass about the wing base gives the position of the centre of mass, and the second radius corresponds to the radius of gyration. The radii are called \`shape parameters' since they are functions only of the normalized shape of the distributions, and they provide a second-order description of the animal morphology. The various radii of wing area are strongly correlated, as are those of wing mass and of virtual mass: the higher radii for each quantity can all be expressed by allometric functions of the first radius. The overall shape of the distribution of a quantity can therefore be characterized by a single parameter, the position of the centroid of that quantity. The strong relations between the radii of wing area, mass and virtual mass hold for a diverse collection of insects, birds and bats. Thus flying animals adhere to \`laws of shape' regardless of biological differences. Aerodynamic and mechanical considerations are most likely to provide an understanding of these laws of shape, but an explanation has proved elusive so far. The detailed shape of a distribution can be reconstructed from the shape parameters by matching the moments of the observed distribution to those of a suitable analytical function. A Beta distribution is compared with the distribution of wing area, i.e. the shape of the wing, and a very good fit is found. With use of the laws of shape relating the higher radii to the first radius, the Beta distribution can be reduced to a function of only one parameter, thus providing a powerful tool for drawing a close approximation to the entire shape of a wing given only its centroid of area. Quite unexpectedly, the continuous spectrum of wing shapes can then be described in detail by a single parameter of shape. <s> BIB002 </s> From Studying Real Hummingbirds to Designing Hummingbird-Like Robots—A Literature Review <s> A. MORPHOLOGY INTRODUCTION OF INSECTS AND FLYER ROBOTICS INSPIRED BY THE INSECTS <s> List Of Color Plates.List Of Boxes.Acknowledgments For Vignettes.Prefaces.1. The Importance And Diversity Of Insects:.What Is Entomology?.The Importance Of Insects.Insect Biodiversity.Insects In Popular Culture And Commerce.Insects As Food.Insect Conservation.2. External Anatomy:.The Cuticle.Segmentation And Tagmosis.The Head.The Thorax.The Abdomen.3. Internal Anatomy And Physiology:.Muscles And Locomotion.The Nervous System And Co-Ordination.The Endocrine System And The Function Of Hormones.The Circulatory System.The Tracheal System And Gas Exchange.The Gut, Digestion And Nutrition.The Excretory System And Waste Disposal.Reproductive Organs.4. Sensory Systems And Behavior:.Mechanical Stimuli.Thermal Stimuli.Chemical Stimuli.Insect Vision.Insect Behavior.5. Reproduction:.Bringing The Sexes Together.Courtship.Sexual Selection.Copulation.Diversity In Genitalic Morphology.Sperm Storage, Fertilization And Sex Determination.Sperm Competition.Oviparity (Egg-Laying).Ovoviviparity And Viviparity.Atypical Modes Of Reproduction.Physiological Control Of Reproduction.6. Insect Development And Life Histories:.Growth.Life-History Patterns And Phases.Process And Control Of Molting.Voltinism.Diapause.Dealing With Environmental Extremes.Migration.Polymorphism And Polyphenism.Age-Grading.Environmental Effects On Development.Climate And Insect Distributions.7. Insect Relationships:.Phylogenetics.The Extant Hexapods.Protura (Proturans), Collembola (Springtails), Diplura (Diplurans).Class Insecta (True Insects).8. Insect Biogeography And Evolution:.Insect Biogeography.The Antiquity Of Insects.Were The First Insects Aquatic Or Terrestrial?.Evolution Of Wings.Evolution Of Metamorphosis.Insect Diversification.Insect Diversification In The Pacific.9. Ground-Dwelling Insects:.Insects Of Litter And Soil.Insects And Dead Trees Or Decaying Wood.Insects And Dung.Insect-Carrion Interactions.Insect-Fungal Interactions.Cavernicolous Insects.Environmental Monitoring Using Ground--Dwelling Hexapods.10. Aquatic Insects:.Taxonomic Distribution And Terminology.The Evolution Of Aquatic Lifestyles.Aquatic Insects And Their Oxygen Supplies.The Aquatic Environment.Environmental Monitoring Using Aquatic Insects.Functional Feeding Groups.Insects Of Temporary Waterbodies.Insects Of The Marine, Intertidal And Littoral Zones.11. Insects And Plants:.Coevolutionary Interactions Between Insects And Plants.Phytophagy (Or Herbivory).Insects And Plant Reproductive Biology.Insects That Live Mutualistically In Specialized Plant Structures.12. Insect Societies:.Subsociality In Insects.Eusociality In Insects.Inquilines And Parasites Of Social Insects.Evolution And Maintenance Of Eusociality.Success Of Eusocial Insects.13. Insect Predation And Parasitism:.Prey/ Host Location.Prey/Host Acceptance And Manipulation.Prey/Host Selection And Specificity.Population Biology - Predator/Parasitoid And Prey/Host Abundance.The Evolutionary Success Of Insect Predation And Parasitism.14. Insect Defense:.Defense By Hiding.Secondary Lines Of Defense.Mechanical Defenses.Chemical Defenses.Defense By Mimicry.Collective Defenses In Gregarious And Social Insects.15. Medical And Veterinary Entomology:.Insect Nuisance And Phobia.Venoms And Allergens.Insects As Causes And Vectors Of Disease.Generalized Disease Cycles.Pathogens.Forensic Entomology.16. Pest Management:.Insects As Pests.The Effects Of Insecticides.Integrated Pest Management (IPM).Chemical Control.Biological Control.Host-Plant Resistance To Insects.Physical Control.Cultural Control.Pheromones And Other Insect Attractants.Genetic Manipulation Of Insect Pests.17. Methods In Entomology: Collecting, Preservation, Curation And Identification:.Collection.Preservation And Curation.Identification.Glossary Of Entomological And Selected Technical Terms.Appendix: A Reference Guide To Orders.Index <s> BIB003 </s> From Studying Real Hummingbirds to Designing Hummingbird-Like Robots—A Literature Review <s> A. MORPHOLOGY INTRODUCTION OF INSECTS AND FLYER ROBOTICS INSPIRED BY THE INSECTS <s> This paper presents the mathematical modeling of flapping flight inch-size micro aerial vehicles (MAVs), namely micromechanical flying insects (MFIs). The target robotic insects are electromechanical devices propelled by a pair of independent flapping wings to achieve sustained autonomous flight, thereby mimicking real insects. In this paper, we describe the system dynamic models which include several elements that are substantially different from those present in fixed or rotary wing MAVs. These models include the wing-thorax dynamics, the flapping flight aerodynamics at a low Reynolds number regime, the body dynamics, and the biomimetic sensory system consisting of ocelli, halteres, magnetic compass, and optical flow sensors. The mathematical models are developed based on biological principles, analytical models, and experimental data. They are presented in the Virtual Insect Flight Simulator (VIFS) and are integrated together to give a realistic simulation for MFI and insect flight. VIFS is a software tool intended for modeling flapping flight mechanisms and for testing and evaluating the performance of different flight control algorithms <s> BIB004 </s> From Studying Real Hummingbirds to Designing Hummingbird-Like Robots—A Literature Review <s> A. MORPHOLOGY INTRODUCTION OF INSECTS AND FLYER ROBOTICS INSPIRED BY THE INSECTS <s> Biology is a useful tool when applied to engineering challenges that have been solved in nature. Here, the emulous goal of creating an insect-sized, truly micro air vehicle is addressed by first exploring biological principles. These principles give insights on how to generate sufficient thrust to sustain flight for centimeter-scale vehicles. Here, it is shown how novel manufacturing paradigms enable the creation of the mechanical and aeromechanical subsystems of a microrobotic device that is capable of Diptera-like wing trajectories. The results are a unique microrobot: a 60 mg robotic insect that can produce sufficient thrust to accelerate vertically. Although still externally powered, this micromechanical device represents significant progress toward the creation of autonomous insect-sized micro air vehicles. <s> BIB005 </s> From Studying Real Hummingbirds to Designing Hummingbird-Like Robots—A Literature Review <s> A. MORPHOLOGY INTRODUCTION OF INSECTS AND FLYER ROBOTICS INSPIRED BY THE INSECTS <s> This paper shows the design and analysis of the actuation mechanism for a four winged flapping wing MAV. The design is set up to exploit resonant properties, as exhibited by flying insects, to reduce the energy expenditure and to provide amplitude amplification. In order to achieve resonance a significantly flexible structure has to be incorporated into the design. The elastic structure used for the body of the MAV is a ring type structure. The ring is coupled to the wings by a compliant amplification mechanism which transforms and amplifies the ring deflection into the large wing root rotation. After initial sizing, the structures are analyzed by finite elements (eigenvalue and transient analysis). Based on the initial analysis, the structures are realized to be tested later. The wings are first analyzed independent of the structure in order to tune wing hinge stiffness to efficiently generate lift, exploiting passive wing pitching. The wings are tuned by using a quasi-steady aerodynamic model. The tuned... <s> BIB006 </s> From Studying Real Hummingbirds to Designing Hummingbird-Like Robots—A Literature Review <s> A. MORPHOLOGY INTRODUCTION OF INSECTS AND FLYER ROBOTICS INSPIRED BY THE INSECTS <s> Insect wings consist of supporting veins and flexible membranes using fibrous composite material. This paper describes a method of wing design and fabrication based on composite, mimicking insect wings through advanced microelectromechanical system (MEMS) technology. SU-8 'fiber' reinforced polydimethylsiloxane (PDMS) membrane forms a fine structure, approaching real wings not only in material conception but also in mechanical performance. Based on a design in its initial stage, a new process was developed integrating all steps into a single procedure. We use a tailored AZ 4562 resist layer as the mold for PDMS wing membrane structuring. A 20 nm hydrophilic oxide layer was grown on the substrate to solve the final lift-off problems which become more severe when the wing membrane gets thinner. The vein thickness can be controlled with high precision by the spin-coating technique. The thickness of artificial membrane can be thinned down to a few microns, thus emulating those of some insects. Our process is compatible with common MEMS technology, and eligible to produce artificial wings of complex geometry and morphology mimicking natural insect wings. Our conclusion is that natural wings can be well mimicked in material conception, weight, venation, size, mass distribution and wing rigidity using hybrid materials. We also show that even using exceedingly compliant material as one composition, composite airfoils can be as light and stiff as insect wings, thereby highlighting the merit of smart material hybridization. <s> BIB007 </s> From Studying Real Hummingbirds to Designing Hummingbird-Like Robots—A Literature Review <s> A. MORPHOLOGY INTRODUCTION OF INSECTS AND FLYER ROBOTICS INSPIRED BY THE INSECTS <s> An electromagnetic MEMS flapping-wing micro air vehicle at insect scale is presented. The detailed scheme, design, micro fabrication and experiment are given in this paper. Firstly, by commercial software ANSYS and MATLAB, electromagnetic analysis, modal analysis and kinetics analysis are proposed. Moreover, based on the result of theoretical analysis, appropriate structure, material and inherent frequency are selected. Then, a new LIGA-like process based on SU-8 photoresist technology is adopted to fabricate thorax, tergum and vein. Finally, a 3.5 cm wingspan, 144 mg weight prototype is integrated, and then we finish the flapping test for this prototype, which has a flapping resonance frequency range of 120–150 Hz. The test result demonstrates the feasibility solution in the development of FMAV based on MEMS, this work is a stepping-stone on the path toward flying robotic insects. <s> BIB008 </s> From Studying Real Hummingbirds to Designing Hummingbird-Like Robots—A Literature Review <s> A. MORPHOLOGY INTRODUCTION OF INSECTS AND FLYER ROBOTICS INSPIRED BY THE INSECTS <s> Dielectric elastomer actuators (DEAs) are attractive for use in bio-inspired flapping-wing robots because they have high work density (specific energy) and can produce a large actuation strain. Although the active membrane of a dielectric elastomer is lightweight, the support structure that pre-tensions the elastomeric membrane is massive and it lowers the overall work density. If the DEA is to be used successfully to drive flapping-wing robots, its support structure must be as lightweight as possible. In this work, we designed, analysed, and developed a lightweight shell using a cross-ply laminate of carbon fibre reinforced polymer (CFRP) to pre-strain a rolled DEA. The CFRP shell was shown to weigh 24.3% of the total mass for the whole DEA assembly, while providing up to 35.0% axial pre-strain to a rolled DEA (BJB-5005 silicone rubber). This DEA assembly using the CFRP shell achieved 30.9% of the theoretical work density for a BJB-TC5005 membrane at 33.5 MV m−1. In comparison, spring rolls with a massive spring core were reported with overall work density merely 10–20% of the maximum value. Furthermore, this CFRP shell can amplify an axial DEA stroke into a larger transverse shell deformation. With these deformation characteristics, this CFRP shell and a rolled DEA were successfully integrated with an insect-inspired thoracic mechanism and they were shown to be feasible to drive it for a flapping wing. <s> BIB009 </s> From Studying Real Hummingbirds to Designing Hummingbird-Like Robots—A Literature Review <s> A. MORPHOLOGY INTRODUCTION OF INSECTS AND FLYER ROBOTICS INSPIRED BY THE INSECTS <s> Flapping-wing micro air vehicles (FWMAVs) are a class of unmanned aircraft that imitate flight characteristics of natural organisms such as birds, bats, and insects, in order to achieve maximum flight efficiency and manoeuvrability. Designing proper mechanisms for flapping transmission is an extremely important aspect for FWMAVs. Compliant transmission mechanisms have been considered as an alternative to rigid transmission systems due to their lower the number of parts, thereby reducing the total weight, lower energy loss thanks to little or practically no friction among parts, and at the same time, being able to store and release mechanical power during the flapping cycle. In this paper, the state-of-the-art research in this field is dealt upon, highlighting open challenges and research topics. An optimization method for designing compliant transmission mechanisms inspired by the thoraxes of insects is also introduced. <s> BIB010 </s> From Studying Real Hummingbirds to Designing Hummingbird-Like Robots—A Literature Review <s> A. MORPHOLOGY INTRODUCTION OF INSECTS AND FLYER ROBOTICS INSPIRED BY THE INSECTS <s> An insect-like tailless flapping wing micro air vehicle (FW-MAV) without feedback control eventually becomes unstable after takeoff. Flying an insect-like tailless FW-MAV is more challenging than flying a bird-like tailed FW-MAV, due to the difference in control principles. This work introduces the design and controlled flight of an insect-like tailless FW-MAV, named KUBeetle. A combination of four-bar linkage and pulley-string mechanisms was used to develop a lightweight flapping mechanism that could achieve a high flapping amplitude of approximately 190°. Clap-and-flings at dorsal and ventral stroke reversals were implemented to enhance vertical force. In the absence of a control surface at the tail, adjustment of the location of the trailing edges at the wing roots to modulate the rotational angle of the wings was used to generate control moments for the attitude control. Measurements by a 6-axis load cell showed that the control mechanism produced reasonable pitch, roll and yaw moments according to the corresponding control inputs. The control mechanism was integrated with three sub-micro servos to realize the pitch, roll and yaw controls. A simple PD feedback controller was implemented for flight stability with an onboard microcontroller and a gyroscope that sensed the pitch, roll and yaw rates. Several flight tests demonstrated that the tailless KUBeetle could successfully perform a vertical climb, then hover and loiter within a 0.3 m ground radius with small variations in pitch and roll body angles. <s> BIB011 </s> From Studying Real Hummingbirds to Designing Hummingbird-Like Robots—A Literature Review <s> A. MORPHOLOGY INTRODUCTION OF INSECTS AND FLYER ROBOTICS INSPIRED BY THE INSECTS <s> Achieving resonance in flapping wings has been recognized as one of the most important principles to enhance power efficiency, lift generation, and flight control performance of high-frequency flapping wing micro air vehicles (MAVs). Most work on the development of such vehicles have attempted to achieve wing flapping resonance. However, the theoretical understanding of its effects on the response and energetics of flapping motion has lagged behind, leading to suboptimal design decisions and misinterpretations of experimental results. In this work, we systematically model the dynamics of flapping wing as a forced nonlinear resonant system, using both nonlinear perturbation method and linear approximation approach. We derived an analytic solution for steady-state flapping amplitude, energetics, and characteristic frequencies including natural frequency, damped natural frequency, and peak frequency. Our results showed that both aerodynamic lift and power efficiency are maximized by driving the wing at natural frequency, instead of other frequencies. Interestingly, the flapping velocity is maximized at natural frequency as well, which can lead to an easy experimental approach to identify natural frequency and validate the resonance design. Our models and analysis were validated with both simulations and experiments on ten different wings mounted a direct-motor-drive flapping wing MAV. The result can serve as a systematic design principle and guidance in the interpretations of empirical results. <s> BIB012 </s> From Studying Real Hummingbirds to Designing Hummingbird-Like Robots—A Literature Review <s> A. MORPHOLOGY INTRODUCTION OF INSECTS AND FLYER ROBOTICS INSPIRED BY THE INSECTS <s> Insects are among the most agile natural flyers. Hypotheses on their flight control cannot always be validated by experiments with animals or tethered robots. To this end, we developed a programmable and agile autonomous free-flying robot controlled through bio-inspired motion changes of its flapping wings. Despite being 55 times the size of a fruit fly, the robot can accurately mimic the rapid escape maneuvers of flies, including a correcting yaw rotation toward the escape heading. Because the robot’s yaw control was turned off, we showed that these yaw rotations result from passive, translation-induced aerodynamic coupling between the yaw torque and the roll and pitch torques produced throughout the maneuver. The robot enables new methods for studying animal flight, and its flight characteristics allow for real-world flight missions. <s> BIB013
Flying insects and hummingbird have a completely distinct construction of apparatus. Insects have a shell or exoskeleton of highly elastic composition material including chitin microfibers embedded in a protein matrix. The insects' thorax can be regarded as a box combining the sides (pleura) and the base (sternum), and the wings are connected to the side by flexible membranes BIB003 . There are two ways to produce flapping in insects via direct or indirect muscles  . Direct muscles are applied to flap their wings for phylogenetically older insects. There are two groups of muscles, the depressors, and the elevators, which contract to move the wing in upstroke and downstroke separately. Direct drive is typical for four-winged insects like dragonflies. Taking dragonfly as an example, wings are directly linked to large muscles within the flight thorax. Elevators muscles attach to the thorax base and connect to the inner side of a pivoted wing base, whereas depressor muscles connect to the outer side of the pivoted wing base. Therefore, elevators muscles and depressor muscles pull wing up and down flapping separately, shown in Fig. 1 -I. Meanwhile, the brain controls each wing independently, which makes very agile flights, but it also restricts their flapping frequency, which is relatively low. The direct muscles of the dragonfly are synchronous muscles. As for phylogenetically modern insects like flies and bees, dorsoventral and longitudinal muscles are the main flight wing-driven muscles. Vertical muscles (Dorsal ventral) connect from the roof-based thorax, whereas longitudinal muscles (Dorsal longitudinal) connect between the anterior (front) and posterior (back) ends of the thorax. They are activated by stretching and deactivated by shortening. All actuations are carried out through the elaborate wing hinge mechanism at the wing root. It means that they operate their wings by deformation of a thorax or the notum (a dorsal part of the thorax). When contracting vertical muscles and lowering thorax roof down directly, wing strokes up. Otherwise, downstroke motion is produced by longitudinal muscles via deforming the thorax roof in a longitudinal direction and raises the thorax roof upward, seen in Fig. 1 -II. The indirect muscles of Dipteran insects are asynchronous muscles. In a word, the indirect muscles power wing movements by varying the elastic thorax's shape. Diagrammatic cross-section of insect flight muscles. I) Thorax mechanisms of direct muscles: A) the wing is stroked up by contracting the elevator muscles; B) the wing is stroked down by shortening the depressor muscles. II) Thorax mechanisms of indirect muscles: A) the wings is stroked up by contracting the vertical muscles pulling the roof down B) by contracting the longitudinal muscles between anterior and posterior ends of a thorax, and elevating up the roof, the wing is stroked down, adapted from BIB010 . The flyers are capable of flapping at much higher frequencies with larger amplitudes for all the wings simultaneously, mainly thanks to the thorax acting as a resonant system. Meanwhile, active wing inversion of insects must originate at the wing base since their wings have no distal joints. Additionally, certain small insects like honeybees and fruit flies, the twist occur very close to the wing root when the wing approaches the end of the stroke, due to the aerodynamics and inertial loads. Also, the wing structure is very light, generally accounting for approximately 1% of the insect's weight BIB002 , which rather differs from hummingbird wing construction. Different insects adapted to different environment and needs, resulting in distinct flight mechanisms such as clap and fling in wasp BIB001 , delayed stall and leadingedge vortex (LEV) in fruitfly and hawkmoth  . Therefore, certain insect-like FWMADs are developed based on these flight mechanisms, such as Micro Mechanical Fly BIB004 , Harvard Robobee BIB005 , KUBeetle BIB011 , DelFly  , TL-Flowerfly  and four wings aerial robotic flapper BIB013 . In addition, certain FWMADs mimicking the insect thorax mechanism were designed such as SU-8 BIB007 , resonant thorax BIB006 , a compliant thoracic mechanism BIB009 - BIB008 . Also, hummingbird-like FWMADs are developed based on the resonance principle BIB012 . 