Flight Capability Research Articles

Control of Hybrid Transitioning Morphing-wing VTOL UAV

Hybrid UAV has combined characteristics of fixed-wing UAV and multi-rotor UAVs. Fixed-wing UAV has higher flight endurance, while the multi-rotor UAV requires no runways and can also perform vertical take-off and landing. Hybrid morphing wing UAV has ability to perform mission both as quadcopter and fixed-wing aircraft combined in efficient manner. This paper discusses the flight capability of a hybrid UAV that can transition between fixed-wing and quadcopter mode of flight. Dynamic equations of the hybrid UAVs are presented. The paper proposes a single non-linear controller with ability to handle the two different flight modes. The proposed controller uses a novel backstepping method and quaternion formulation, as transition between Euler angles provides problems like singularities. Although, backstepping has been used in various control design,it is unique to use backstepping that handles the complex vehicle transition phase along with use of quaternions. The performance of the proposed scheme is demonstrated via numerical simulations.

Extended incremental non-linear control allocation (XINCA) for quadplanes

Hybrid UAVs have gained a lot of interest for their combined vertical take-off & landing (VTOL) and efficient forward flight capabilities. But their control is facing challenges in over-actuation and conflicting requirements depending on the flight phase which can easily lead to actuator saturation. Incremental Non-linear Control Allocation (INCA) has been proposed to solve the platform’s control allocation problem in the case of saturation or over-actuation by minimizing a set of objective functions. This work demonstrates INCA on quadplanes, an in-plane combination between a quadrotor and a conventional fixed-wing, and proposes an extension to control the outer loop. The novel controller is called Extended INCA (XINCA) and adds the wing orientation as a force-generating actuator in the outerloop control optimization. This leads to a single controller for all flight phases that avoids placing the wing at negative angles of attack and minimizes the load on hover motors. XINCA has low dependence on accurate vehicle models and requires only several optimization parameters. Flight simulations and experimental flights are performed to demonstrate the performance.

Trade-off between flight capability and reproduction in Acridoidea (Insecta: Orthoptera).

In many insect taxa, there is a well‐established trade‐off between flight capability and reproduction. The wing types of Acridoidea exhibit extremely variability from full length to complete loss in many groups, thus, provide a good model for studying the trade‐off between flight and reproduction. In this study, we completed the sampling of 63 Acridoidea species, measured the body length, wing length, body weight, flight muscle weight, testis and ovary weight, and the relative wing length (RWL), relative flight muscle weight (RFW), and gonadosomatic index (GSI) of different species were statistically analyzed. The results showed that there were significant differences in RWL, RFW, and GSI among Acridoidea species with different wing types. RFW of long‐winged species was significantly higher than that of short‐winged and wingless species (p < .01), while GSI of wingless species was higher than that of long‐winged and short‐winged species. The RWL and RFW had a strong positive correlation in species with different wing types (correlation coefficient r = .8344 for male and .7269 for female, and p < .05), while RFW was strong negatively correlated with GSI (r = −.2649 for male and −.5024 for female, and p < .05). For Acridoidea species with wing dimorphism, males with relatively long wings had higher RFW than that of females with relatively short wings, while females had higher GSI. Phylogenetic comparative analysis showed that RWL, RFW, and GSI all had phylogenetic signals and phylogenetic dependence. These results revealed that long‐winged individuals are flight capable at the expense of reproduction, while short‐winged and wingless individuals cannot fly, but has greater reproductive output. The results support the trade‐off between flight and reproduction in Acridoidea.

Global dispersal and diversification in ground beetles of the subfamily Carabinae

The origin and diversification process of lineages of organisms that are currently widely distributed among continents is an interesting subject for exploring the evolutionary history of global species diversity. Ground beetles of the subfamily Carabinae are flightless except for one lineage, but nevertheless occur on all continents except Antarctica. Here, we used sequence data from ultraconserved elements to reconstruct the phylogeny, divergence time, biogeographical history, ancestral state of hind wings and changes in the speciation rate of Carabinae. Our results show that Carabinae originated in the Americas and diversified into four tribes during the period from the late Jurassic to the late Cretaceous, with two in South America (Celoglossini) and Australasia (Pamborini) and two in Laurasia (Cychrini and Carabini). The ancestral Carabinae were inferred to be winged; three of four tribes (Cychrini, Ceglossini and Pamborini) have completely lost their hind wings and flight capability. The remaining tribe, Carabini, diverged into the subtribes Carabina (wingless) and Calosomina (winged) in the Oligocene. Carabina originated in Europe, spread over Eurasia and diversified into approximately 1000 species, accounting for around 60% of all Carabinae species. Calosomina that were flight-capable dispersed from North America or Eurasia to South America, Australia, and Africa, and then flightless lineages evolved on oceanic islands and continental highlands. The speciation rate increased in the Cychrini and Carabini clades in Eurasia. Within Carabini, the speciation rate was higher for wingless than winged states. Our study showed that the global distribution of Carabinae resulted from ancient dispersal before the breakup of Gondwana and more recent dispersal through flight around the world. These patterns consequently illustrate the causal relationships of geographical history, evolution of flightlessness, and the global distribution and species diversity of Carabinae.

The effects of temephos, permethrin and malathion selection on the fitness and fecundity of Aedes aegypti

The recent scale-up of insecticide use has led to the rapid spread of insecticide resistance (IR) in mosquito populations across the world. Previous work has suggested that IR mechanisms could influence mosquito life-history traits, leading to alterations in fitness and key physiological functions. This study investigates to what extent mosquito fitness may be affected in a colony of Aedes aegypti after selection with temephos, permethrin or malathion insecticides. We measured immature development, sex ratio, adult longevity, energetic reserves under different rearing conditions and time points, ingested bloodmeal volume, mosquito size, male and female reproductive fitness and flight capability in the unexposed offspring of the three selected strains and unselected strain. We found that insecticide selection does have an impact on mosquito fitness traits in both male and female mosquitoes, with our temephos-exposed strain showing the highest immature development rates, improved adult survival, larger females under crowded rearing and increased sperm number in males. In contrast, this strain showed the poorest reproductive success, demonstrating that insecticide selection leads to trade-offs in life-history traits, which have the potential to either enhance or limit disease transmission potential.

Harbor-border inspection for unmanned aerial vehicle based on visible light source tracking.

The unmanned aerial vehicle (UAV) offers unique advantages of autonomous flight capability and small coefficient of risk, and is increasingly being used in harbor-border inspection to ensure security and orderly operation of harbors. In response to the influence of external factors such as electromagnetic interference in harbor-border inspection, this paper utilizes UAV and visible light communication (VLC) to build an efficient system to track maritime targets near the harbor reliably. In a VLC scenario, a geometrical equation for transmitter positioning is first proposed based on the received signal strength of the optical signal emitted by the target. On this basis, linear iterative positioning (LIP) using first-order Taylor expansion is proposed to realize online beam tracking. Furthermore, quadratic approximative iterative positioning (QAIP), a more precise approximation of the geometrical equation, is proposed based on second-order Taylor expansion. Simulation results show that the proposed algorithms can track targets effectively, and QAIP can achieve higher accuracy with no noise or high signal-to-noise ratio. In addition, compared with the geometrical solution, LIP and QAIP have faster computing speeds and fixed overheads.

The evolution of tinamous (Palaeognathae: Tinamidae) in light of molecular and combined analyses

Abstract The Neotropical tinamous are of particular interest in our efforts to understand the evolution of modern birds. They inhabit both forested and open environments and, although volant, have limited flight capabilities. Numerous studies have recognized the monophyly of tinamous and their relationships either as sister to the flightless ratites (ostriches, emus and their relatives) or within the ratites themselves. Despite the numerous bird phylogenies published recently, modern investigations of relationships within the tinamous themselves have been limited. Here, we present the first detailed phylogenetic analysis and divergence-date estimation including a significant number of tinamou species, both extant and fossil. The monophyly of most currently recognized polytypic genera is recovered with high support, with the exception of the paraphyletic Nothura and Nothoprocta. The traditional subdivision between those tinamous inhabiting open areas (Nothurinae) and forest environments (Tinaminae) is also confirmed. A temporal calibration of the resultant phylogeny estimates that the basal divergence of crown Tinamidae took place between 31 and 40 Mya.

The link between avian brachial index, flight capability and the neornithine evolutionary radiation.

In dictating the relative distances between the elbow, shoulder and wrist, avian brachial index (BI=humerus/radius-ulna length) likely influences wing kinematics and, therefore, might predict extinct avian flight capability. This underpins the hypothesis that non-neornithine Mesozoic avialans with relatively low BIs (associated with improved flight capabilities) restricted neornithine diversification until after the Cretaceous-Paleogene boundary. Here, correlations between flight metrics (wingbeat frequency (f), stroke angle (θ), wing loading (Q) and aspect ratio) and BI were investigated and vice versa. Additionally, the evolutionary model best describing the phylogenetic distribution of BI, and the temporal patterns in BI, flight metrics, body mass (Mb ), and size-corrected humerus (Lh ) and radius-ulna (Lru ) length were determined. BI was best described by Ornstein-Uhlenbeck processes, with low α values indicating a gradual shift towards a future theoretical optimum. BI also decreased overall through evolutionary time with the flight metrics mirroring temporal patterns of change in BI. Mb , Lh and Lru overall decreased apart from increases in Lh and Lru following the middle-late Miocene (also leading to BI increasing) due to diversifications of the Anatinae and Sphenisciformes. Lh overall decreased further than Lru. Consequently, decreasing Lh mainly contributed to decreasing BI through evolutionary time, implying flight performance increased through neornithine evolution. However, the timings of radiations in these variables implies an Eocene radiation of neornthine flight ecology rather than a rapid expansion into niches vacated by non-neornithine Mesozoic avialians following the Cretaceous-Paleogene boundary. Multiple regressions showed f, θ and Q explained 60% of variation in BI. However, unequivocally evaluating whether BI is related to wing movement (and flight capability) requires direct measures of wing movement for many species, which are currently unavailable. Finally, the findings here and previously observed clade-specificity in BI, suggest flight ecology may also be clade-specific. Hence, the utility of phylogeny in predicting flight ecology requires exploration.

The function of the alula with different geometric parameters on the flapping wing

Birds in nature have the ability to maintain high aerodynamic efficiency in complex flight conditions. This agility stems from the multi-degree-of-freedom flapping motion and specialized feather systems that evolved over millions of years. The leading-edge alula is considered a typical feather system that can enhance the flight envelope and capabilities of birds at low speed and high incidence. Previous studies usually adopted a static model, ignoring unsteady effects caused by flapping motion. Thus, we numerically investigated the function of the alula with different geometric parameters on the flapping wing in this paper. The alula has both the slot effect and vortex generator effect during the flapping motion, whereas the effect that plays a main role in lift enhancement changes as time varies. At the beginning of the upstroke, the slot effect plays the main role. At mid-time of the upstroke, the vortex generator effect plays the main role. Different geometric parameters have different influences on these two effects. The dimensionless spanwise location affects the strength of both the ATEV (alula trailing edge vortex) and ASV (alula streamwise vortex). The relative angle affects mainly the strength of the ATEV, whereas the deflection angle affects mainly the strength of the ASV. The optimal geometric parameters to obtain maximum lift enhancement are a dimensionless spanwise location of 0.5, a relative angle of 0°, and a deflection angle of 10°, with a lift enhancement of 5.5% compared to the baseline wing.

A lightweight magnetic gripper for an aerial delivery vehicle: design and applications

&lt;p&gt;In recent years, drones have become widely used in many fields. Their vertical flight capability makes these systems suitable for carrying out a variety of tasks. In this paper, the delivery service they provide is analysed. The delivery of goods quickly and to remote areas is a relevant application scenario; however, the systems proposed in the literature use electromagnets, which affect the duration of the flight. In addition, these devices are heavy and suffer from high energy consumption, which reduces the maximum transportable payload. This study proposes a new lightweight magnetic plate composed of permanent magnets, capable of collecting and positioning any object as long as it has a ferromagnetic surface on the top. This plate was developed for the Mohamed Bin Zayed International Robotics Challenge 2020, an international robotics competition for multi-robot systems. Challenge two of this competition required a drone capable of picking up different types of bricks and assembling them to build a wall according to an assigned pattern. The bricks were of different colours and sizes, with weights ranging from 1 to 2 kg. In light of this, it was concluded that weight was the most relevant specification to consider in drone design.&lt;/p&gt;

Custer Channel Wings for Short Takeoff and Landing of Unmanned Aircraft

The channel wing is a lift-enhancement concept pioneered by Willard Ray Custer in the late 1940s in an effort to provide a fixed-wing aircraft with short takeoff and landing (STOL) capabilities. This paper experimentally investigates the possibility of using Custer channel wings for slow flight and STOL of small (under 35 kg) fixed-wing unmanned aerial vehicles. The Custer unmanned aircraft developed at the University of Southampton is introduced in this paper, including details of the installed channel wings and other systems necessary for slow-flight operation. Results from wind-tunnel tests are presented, showing a significant lift increase due to the channel wings in the range of airspeeds of interest. Flight tests are carried out to demonstrate the slow flight and STOL capabilities of the aircraft, showing superior stall characteristics and a two-thirds reduction of the runway length required when using the channel wings. Flight-test comparisons to a conventional wing–propeller configuration show superior slow-flight performance and 7–9% lower cruise speed of the channel-wing aircraft.

Quadrotor Controller Design Techniques and Applications Review

Rotor-craft style UAV, such as the quadrotor, has become increasingly popular with researchers due to its advantages over fixed-wing UAV. The quadrotor is highly maneuverable, can perform vertical take-off and landing (VTOL), and can hover flight capability. Nevertheless, handling the quadrotor complex, highly nonlinear dynamics is difficult and challenging. A suitable control system is needed to control the quadrotor system effectively. Therefore, this paper presents a review of different controller design techniques used by researchers over the past years for the quadrotor rotational and translational stabilization control. Three categories are discussed: linear controller, nonlinear controller, and intelligent controller. Based on their performance specifications, the system rise time, settling time, overshoot, and steady-state error are discussed. Finally, a comparative analysis is tabulated, summarizing the literature in the performance specifications described above.

The relationship between body size and flight power output in the mango stem borer (Batocera rufomaculata)

Adult body size in insects can be influenced by environmental conditions during larval growth. The effect of such intraspecific variation in body mass on flight performance is poorly understood. In Batocera rufomaculata, a large tree boring beetle, adults emerging from larvae that developed in a dying host tree, and therefore, under nutrient-deprived diet conditions, are smaller but have an elevated long-distance flight capability compared to larger conspecifics that developed in viable host trees. The improved endurance for long-distance flight in the smaller individuals appears to contradict the interspecific trend in flying animals of a decrease in Cost of Transport (CoT) with increased body mass. To explore the relationship between intraspecific variation in body size and power expended during steady forward flight, we flew these beetles tethered in a wind tunnel and compared the flapping kinematics and power output of individuals varying in body mass (1–7 gr). Concurrently, we measured the forces the insects applied on the tether allowing us to evaluate the tethering effects and correct for them. From the flapping kinematics we estimated the mechanical power expended using a quasi-steady blade-element model. We found that muscle mass-specific power did not differ between small and large individuals flying at the same wind (flight) speed in the tunnel. Consequently, the CoT of B. rufomaculata does not vary with body mass. Such invariance of mass-specific power with body mass may aid the dispersal of smaller individuals from deteriorating host trees to new ones.

Design, Assembly and Testing of a Mobile Laboratory Based on a VTOL Scale Motorglider

The objective of this paper is to explain the design steps and performance analysis of a vertical take-off and landing (VTOL) unmanned air vehicle (UAV) based on a Pilatus B4 glider scale model. Energy consumption, forces and thrust analyses are carry out to determinate the perfect match between low take-off weight and high aerodynamic performance. As a first approach a complete analysis of glider aerodynamic performances are settle to understand and design a proper support for VTOL conversion. Longitudinal static stability is fulfilled by evaluating the center of gravity location with respect to neutral position, nevertheless dynamic stability, and V-n diagram in VTOL configuration are evaluated to guarantee a correct behavior during fixed wing flight mode. In addition, power requirements, motor thrust capability and tilt-motors servo assisted system performance are determinate in perspective of flight performance to find out the perfect transition from multirotor take-off and landing mode to fixed-wing flying state. For these purposes a test bench has being designed to evaluate thrust, electrical absorption and rpm motor behavior along the throttle range. Finally, the assembly and preliminary tests are performed in order to validate the VTOL and Forward flight capability.

Simulation and Characterization of Wind Impacts on sUAS Flight Performance for Crash Scene Reconstruction

Small unmanned aircraft systems (sUASs) have emerged as promising platforms for the purpose of crash scene reconstruction through structure-from-motion (SfM) photogrammetry. However, auto crashes tend to occur under adverse weather conditions that usually pose increased risks of sUAS operation in the sky. Wind is a typical environmental factor that can cause adverse weather, and sUAS responses to various wind conditions have been understudied in the past. To bridge this gap, commercial and open source sUAS flight simulation software is employed in this study to analyze the impacts of wind speed, direction, and turbulence on the ability of sUAS to track the pre-planned path and endurance of the flight mission. This simulation uses typical flight capabilities of quadcopter sUAS platforms that have been increasingly used for traffic incident management. Incremental increases in wind speed, direction, and turbulence are conducted. Average 3D error, standard deviation, battery use, and flight time are used as statistical metrics to characterize the wind impacts on flight stability and endurance. Both statistical and visual analytics are performed. Simulation results suggest operating the simulated quadcopter type when wind speed is less than 11 m/s under light to moderate turbulence levels for optimal flight performance in crash scene reconstruction missions, measured in terms of positional accuracy, required flight time, and battery use. Major lessons learned for real-world quadcopter sUAS flight design in windy conditions for crash scene mapping are also documented.

Domestic egg-laying hens, Gallus gallus domesticus, do not modulate flapping flight performance in response to wing condition.

Wild birds modulate wing and whole-body kinematics to adjust their flight patterns and trajectories when wing loading increases flight power requirements. Domestic chickens (Gallus gallus domesticus) in backyards and farms exhibit feather loss, naturally high wing loading, and limited flight capabilities. Yet, housing chickens in aviaries requires birds to navigate three-dimensional spaces to access resources. To understand the impact of feather loss on laying hens' flight capabilities, we symmetrically clipped the primary and secondary feathers before measuring wing and whole-body kinematics during descent from a 1.5 m platform. We expected birds to compensate for increased wing loading by increasing wingbeat frequency, amplitude and angular velocity. Otherwise, we expected to observe an increase in descent velocity and angle and an increase in vertical acceleration. Feather clipping had a significant effect on descent velocity, descent angle and horizontal acceleration. Half-clipped hens had lower descent velocity and angle than full-clipped hens, and unclipped hens had the highest horizontal acceleration. All hens landed with a velocity two to three times greater than in bird species that are adept fliers. Our results suggest that intact laying hens operate at the maximal power output supported by their anatomy and are at the limit of their ability to control flight trajectory.

Comparative Validation Study on Bioinspired Morphology-Adaptation Flight Performance of a Morphing Quad-Rotor

Inspired by the advantages from natural birds' shape-morphing adapted flight performance, this work investigates how the bioinspired adaptative morph induced inertia variation affects the flight performance of a morphing quad-rotor. Extensive numerical and experimental evaluations on a custom-built morphing quad-rotor that is steered along a predefined path and hovers in the presence of constant wind disturbance were performed and analyzed. Simulation results demonstrate that the smaller quad-rotor exhibits better agility performance due to the compact volume/size and lower weight, while the bigger one appears more flight robustness in a disturbed environment such as windy testing area. Experimental studies further prove that by adaptatively altering its volume/size, our quad-rotor with the bioinspired in-flight morphing behavior can well execute path following tasks in a constrained space without deviating the trajectory when encountering obstacles, as well it can withstand external wind torque through morphing up its volume to therewith increase relevant moment-of-inertia for improving the flight robustness. Compared to the regular scaled aerial vehicles whose volumes' change follows a weight change proportionally, our results also indicate that our in-flight morphing aerial vehicle mechanism (i.e. the quad-rotor morphs the volume but without changing weight/mass) shows more advantages in power efficiency and morphologically adaptative flight capability.

Conversion control of a tilt tri-rotor unmanned aerial vehicle with modeling uncertainty

The tilt-rotor unmanned aerial vehicle (TRUAV) has vertical take-off and landing and high-speed flight capabilities through conversion and reconversion modes, thereby presenting wide application prospects. This article presents a compact tilt tri-rotor UAV. For flying in the conversion mode, the TRUAV needs to realize the transition of two control logic and two kinds of actuators in both of the rotor and fixed-wing modes, achieving the control of the multi-input multioutput, input nonaffine, and nonlinear multichannel cross-coupling UAV system. Furthermore, the lateral dynamics of a tilt tri-rotor UAV is more unstable for unpaired rotors. These system characteristics present a great challenge to conversion control. To solve these problems, the nonlinear dynamic model of the vehicle in the conversion mode is provided. Furthermore, a cascade control system consisting of position control, velocity control, angle control, angular velocity control, and control mixer is proposed. The simulation result of the control system shows steady flight and a fast transition in the conversion mode with modeling uncertainty in case of no wind.

Loss of Fis1 impairs proteostasis during skeletal muscle aging in Drosophila.

Increased levels of dysfunctional mitochondria within skeletal muscle are correlated with numerous age‐related physiopathological conditions. Improving our understanding of the links between mitochondrial function and muscle proteostasis, and the role played by individual genes and regulatory networks, is essential to develop treatments for these conditions. One potential player is the mitochondrial outer membrane protein Fis1, a crucial fission factor heavily involved in mitochondrial dynamics in yeast but with an unknown role in higher‐order organisms. By using Drosophila melanogaster as a model, we explored the effect of Fis1 mutations generated by transposon Minos‐mediated integration. Mutants exhibited a higher ratio of damaged mitochondria with age as well as elevated reactive oxygen species levels compared with controls. This caused an increase in oxidative stress, resulting in large accumulations of ubiquitinated proteins, accelerated muscle function decline, and mitochondrial myopathies in young mutant flies. Ectopic expression of Fis1 isoforms was sufficient to suppress this phenotype. Loss of Fis1 led to unbalanced mitochondrial proteostasis within fly muscle, decreasing both flight capabilities and lifespan. Fis1 thus clearly plays a role in fly mitochondrial dynamics. Further investigations into the detailed function of Fis1 are necessary for exploring how mitochondrial function correlates with muscle health during aging.

Prenatal Developmental Trajectories of Fluctuating Asymmetry in Bat Humeri.

Fluctuating asymmetry (random fluctuations between the left and right sides of the body) has been interpreted as an index to quantify both the developmental instabilities and homeostatic capabilities of organisms, linking the phenotypic and genotypic aspects of morphogenesis. However, studying the ontogenesis of fluctuating asymmetry has been limited to mostly model organisms in postnatal stages, missing prenatal trajectories of asymmetry that could better elucidate decoupled developmental pathways controlling symmetric bone elongation and thickening. In this study, we quantified the presence and magnitude of asymmetry during the prenatal development of bats, focusing on the humerus, a highly specialized bone adapted in bats to perform under multiple functional demands. We deconstructed levels of asymmetry by measuring the longitudinal and cross-sectional asymmetry of the humerus using a combination of linear measurements and geometric morphometrics. We tested the presence of different types of asymmetry and calculated the magnitude of size-controlled fluctuating asymmetry to assess developmental instability. Statistical support for the presence of fluctuating asymmetry was found for both longitudinal and cross-sectional asymmetry, explaining on average 16% of asymmetric variation. Significant directional asymmetry accounted for less than 6.6% of asymmetric variation. Both measures of fluctuating asymmetry remained relatively stable throughout ontogeny, but cross-sectional asymmetry was significantly different across developmental stages. Finally, we did not find a correspondence between developmental patterns of longitudinal and cross-sectional asymmetry, indicating that processes promoting symmetrical bone elongation and thickening work independently. We suggest various functional pressures linked to newborn bats’ ecology associated with longitudinal (altricial flight capabilities) and cross-sectional (precocial clinging ability) developmental asymmetry differentially. We hypothesize that stable magnitudes of fluctuating asymmetry across development could indicate the presence of developmental mechanisms buffering developmental instability.