Wing Kinematic Parameters Research Articles

Development of a Novel Tailless X-Type Flapping-Wing Micro Air Vehicle with Independent Electric Drive

A novel tailless X-type flapping-wing micro air vehicle with two pairs of independent drive wings is designed and fabricated in this paper. Due to the complexity and unsteady of the flapping wing mechanism, the geometric and kinematic parameters of flapping wings significantly influence the aerodynamic characteristics of the bio-inspired flying robot. The wings of the vehicle are vector-controlled independently on both sides, enhancing the maneuverability and robustness of the system. Unique flight control strategy enables the aircraft to have multiple flight modes such as fast forward flight, sharp turn and hovering. The aerodynamics of the prototype is analyzed via the lattice Boltzmann method of computational fluid dynamics. The chordwise flexible deformation of the wing is implemented via designing a segmented rigid model. The clap-and-peel mechanism to improve the aerodynamic lift is revealed, and two air jets in one cycle are shown. Moreover, the dynamics experiment for the novel vehicle is implemented to investigate the kinematic parameters that affect the generation of thrust and maneuver moment via a 6-axis load cell. Optimized parameters of the flapping wing motion and structure are obtained to improve flight dynamics. Finally, the prototype realizes controllable take-off and flight from the ground.

Application of a novel deep learning-based 3D videography workflow to bat flight.

Studying the detailed biomechanics of flying animals requires accurate three-dimensional coordinates for key anatomical landmarks. Traditionally, this relies on manually digitizing animal videos, a labor-intensive task that scales poorly with increasing framerates and numbers of cameras. Here, we present a workflow that combines deep learning-powered automatic digitization with filtering and correction of mislabeled points using quality metrics from deep learning and 3D reconstruction. We tested our workflow using a particularly challenging scenario: bat flight. First, we documented four bats flying steadily in a 2 m3 wind tunnel test section. Wing kinematic parameters resulting from manually digitizing bats with markers applied to anatomical landmarks were not significantly different from those resulting from applying our workflow to the same bats without markers for five out of six parameters. Second, we compared coordinates from manual digitization against those yielded via our workflow for bats flying freely in a 344 m3 enclosure. Average distance between coordinates from our workflow and those from manual digitization was less than a millimeter larger than the average human-to-human coordinate distance. The improved efficiency of our workflow has the potential to increase the scalability of studies on animal flight biomechanics.

Wing geometry and kinematic parameters optimization of bat-like robot fixed-altitude flight for minimum energy

In this paper, the geometry parameters (WGP) and kinematic parameters (WKP) of bat wings are optimized by using the revised quasi-steady aerodynamic model and genetic particle swarm optimization algorithm (GPSO) according to the structural characteristics and kinematic law of bat, to meet the requirement of minimum flapping energy and improve the endurance of bat-like robot. For the first time, the dynamic model of bat flapping motion is improved by considering the effects of active deformation, passive flexible deformation, gravity moment, and inertia moment of the wing structure. Based on the power density model, the optimization objective function is established, and the lift-weight ratio (LtoW), Reynolds number (Re), aspect ratio (AR), Strouhal number (St), and boundary constraints of each parameter are added to complete the optimization of WGP and WKP. The optimized aerodynamic forces and power densities are compared with the estimates for actual bats flying at a fixed-altitude, and the results showed that the optimized parameters resulted in more stable aerodynamic forces and reduced energy consumption by half. Finally, the sensitivity analysis of the influence of each parameter on the LtoW and power density is carried out to better understand the effect of each parameter on keeping fixed-altitude flight and reducing energy consumption. This study can provide the theoretical basis for reasonable parameter design of bat-like robot.

Optimization of a Twistable Hovering Flapping Wing Inspired by Giant Hummingbirds Using the Unsteady Blade Element Theory

Due to the complexity of tailoring the wing flexibility and selecting favorable kinematics, the design of flapping wings is a considerably challenging problem. Therefore, there is an urgent need to investigate methods that can be used to design wings with high energy efficiency. In this study, an optimization model was developed to improve energy efficiency by optimizing wing geometric and kinematic parameters. Then, surrogate optimization was used to solve the design optimization model. Finally, the optimal design parameters and the associated sensitivity were provided. The optimized flapping wing, inspired by hummingbirds, features large geometrical parameters, a moderate amplitude of the flapping angle, and low frequency. With the spanwise twisting deformation considered in the parameterization model, the optimization solver gave an optimized wing with a pitching amplitude of approximately 39 deg at the root and 76 deg at the tip. According to the sensitivity analysis, the length of the wing, flapping frequency, and flapping amplitude are the three critical parameters that determine both force generation and power consumption. The amplitude of the pitching motion at the wing root contributes to lowering power consumption. These results provide some guidance for the optimal design of flapping wings.

Sensitivity Analysis of Wing Geometric and Kinematic Parameters for the Aerodynamic Performance of Hovering Flapping Wing

The wing planform and flapping kinematics are critical for the hovering flight of flapping wing micro air vehicles (FWMAVs). The degree of influence of wing geometry and kinematic parameters on aerodynamic performance still lacks in-depth analysis. In this study, a sensitivity analysis was conducted based on the quasi-steady aerodynamic model. Each parameter was investigated independently by using the control variable method. The degree of each variable’s influence on lift, power, and power loading is evaluated and compared. Furthermore, detailed exponential relationships were established between the parameters and the corresponding aerodynamic properties. It is found that, for the geometric parameters, wing area has the greatest influence on lift, and the distribution of area has the most visible effect on aerodynamic power. All geometric parameters are negatively correlated with power loading. For the kinematic parameters, flapping frequency, compared with sweeping amplitude, results in faster lift growth and slower drop in power loading, while their influence on aerodynamic power is nearly comparable. A moderate pitching amplitude with advanced rotation will maximize the lift. For the flapping trajectory, lift and power loading are primarily affected by the shape of the pitching motion rather than the sweeping motion. But the sweeping motion seems to dominate the power consumption. The research in this paper is helpful to understand the effect of each parameter and provide theoretical guidance for the development of FWMAVs.

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.

Wing geometry and kinematic parameters optimization of flapping wing hovering flight for minimum energy

The optimizations of wing geometry parameters (WGP) and wing kinematic parameters (WKP) to minimize the energy consumption of flapping wing hovering flight are performed by using a revised quasi-steady aerodynamic model and hybrid genetic algorithm (hybrid-GA). The parametrization method of dynamically scaled wing with the non-dimensional conformal feature of fruit fly's wing is firstly developed for the optimization involving the WGP. And the objective function of optimization is formed on basis of the power density model with the additional penalty items of lift-to-weight ratio, boundary constraints, aspect ratio (AR) and Reynolds number (Re). The obtained optimal WGP and WKP are separately substituted into the power density model to estimate the instantaneous forces and the power output again. The lower power density, flapping frequency and larger WGP for the combined optimal WGP and WKP are obtained in comparison with the estimated values for hovering fruit fly. These results might arise from the effect of strong coupling relationship between WGP and WKP via AR and Re on minimization of power density under the condition of lift balancing weight. Moreover, the optimal flapping angle manifests the harmonic profile, and the optimal pitch angle possesses the round trapezoidal profile with certain faster time scale of pitch reversal. The conceptual model framework of combined optimization provides a useful way to design fundamental parameters of biomimic flapping wing micro aerial vehicle.

Wing Geometry and Kinematic Parameters Optimization of Flapping Wing Hovering Flight

How to efficiently mimic the wing shape and kinematics pattern of an able hovering living flier is always a concern of researchers from the flapping wing micro aerial vehicles community. In this work, the separate or combined optimizations of wing geometry or/and wing kinematic parameters are systematically performed to minimize the energy of hovering flight, firstly on the basis of analytically extended quasi-steady aerodynamic model by using hybrid genetic algorithm. Before the elaboration of the optimization problem, the parametrization description of dynamically scaled wing with non-dimensional conformal feature of insect-scale rigid wing is firstly proposed. The optimization results show that the combined optimization of wing geometry and kinematic parameters can obtain lower flapping frequency, larger wing geometry parameters and lower power density in comparison with those from other cases of optimization. Moreover, the flapping angle for the optimization involving wing kinematic parameters manifests harmonic shape profile and the pitch angle possesses round trapezoidal profile with certain faster time scale of pitch reversal. The combined optimization framework provides a novel method for the conceptual design of fundamental parameters of biomimetic flapping wing micro aerial vehicle.

Adaptive attitude and position control of an insect-like flapping wing air vehicle

This study describes an adaptive sliding mode technique for attitude and position control of a rigid body insect-like flapping wing model in the presence of uncertainties. For this purpose, a six-degrees-of-freedom nonlinear and time-varying dynamic model of a typical hummingbird is considered for simulation studies. Based on the quasi-steady assumptions, three major aerodynamic loads including delayed stall, rotational lift and added mass are presented and analyzed, respectively. Using the averaging theory, a time-varying system is then transformed into the time-invariant system to design the adaptive controller. The controller is designed so that the closed-loop system will follow any desired trajectory without prior information about uncertainties. In the final stage, in order to find the wing kinematic parameters and to ensure the feasibility of the control commands, two feedforward artificial neural networks are developed and trained using aerodynamic forces and moments from the open-loop simulation data. In comparison with non-adaptive technique, it is shown that the adaptive sliding mode controller is able to stabilize the vehicle in the presence of input disturbances and model uncertainties.

The numerical simulation of the wing kinematics effects on near wake topology and aerodynamic performance in hovering Drosophila flight

The parallel large-scale unstructured finite volume method based on an Arbitrary Lagrangian–Eulerian (ALE) formulation in Erzincanli and Sahin (2013) has been employed in order to investigate the effects of the wing kinematics on the near wake topology produced by a pair of flapping Drosophila wings in hover flight. The three-dimensional wing shape and the baseline wing kinematics are the same as those of the robotic fly by Dickinson et al. (1999). The simulations are used to quantify the important wing kinematic parameters for the wake topology and as well as their correlations with the force production. The angle-of-attack is shown to be very effective for producing lift during the wing translational motion. However, for larger values the angle-of-attack limits the angle during the stroke reversal and reduces the rotational lift. The angle-of-attack at which the maximum lift coefficient occurs is in excellent agreement with the earlier experiments in the literature. In addition, the numerical results confirm that the increase in the wing stroke amplitude leads to a prolonged attachment of the leading edge vortex (LEV) over a relatively large distance and increases force production. The variations in the heave angle include the figure-of-eight pattern, figure-of-O pattern and figure-of-U pattern. The constant heave angle and figure-of-eight pattern are found to have a more profound influence on the magnitude of force production. In addition, some asymmetric variations in the wing kinematics are introduced in order to assess the important parameters determining forward and backward flights. The paddling wing motion is shown to be very effective to initiate forward and backward acceleration.

Adjoint-Based Optimization of Three-Dimensional Flapping-Wing Flows

Optimization of the three-dimensional unsteady viscous flow near a flapping wing in hover is performed using a time-dependent adjoint-based methodology. The sensitivities of a penalized lift coefficient to wing shape and kinematic parameters are computed using a time-dependent discrete-adjoint formulation. The unsteady discrete-adjoint equations required for the calculation of the sensitivity derivatives are integrated backward in time over the entire interval of interest. The gradient of the objective functional obtained using the adjoint formulation is then used to update the values of shape and kinematic design variables. The efficiency of this adjoint-based methodology is demonstrated by optimizing the shape and kinematics of a hovering wing. The numerical results show that the highest improvement in the wing performance is obtained by using combined optimization of the wing shape and kinematics.

Kinematic control of aerodynamic forces on an inclined flapping wing with asymmetric strokes

In the present study, we conduct an experiment using a one-paired dynamically scaled model of an insect wing, to investigate how asymmetric strokes with different wing kinematic parameters are used to control the aerodynamics of a dragonfly-like inclined flapping wing in still fluid. The kinematic parameters considered are the angles of attack during the mid-downstroke (αmd) and mid-upstroke (αmu), and the duration (Δτ) and time of initiation (τp) of the pitching rotation. The present dragonfly-like inclined flapping wing has the aerodynamic mechanism of unsteady force generation similar to those of other insect wings in a horizontal stroke plane, but the detailed effect of the wing kinematics on the force control is different due to the asymmetric use of the angle of attack during the up- and downstrokes. For example, high αmd and low αmu produces larger vertical force with less aerodynamic power, and low αmd and high αmu is recommended for horizontal force (thrust) production. The pitching rotation also affects the aerodynamics of a flapping wing, but its dynamic rotational effect is much weaker than the effect from the kinematic change in the angle of attack caused by the pitching rotation. Thus, the influences of the duration and timing of pitching rotation for the present inclined flapping wing are found to be very different from those for a horizontal flapping wing. That is, for the inclined flapping motion, the advanced and delayed rotations produce smaller vertical forces than the symmetric one and the effect of pitching duration is very small. On the other hand, for a specific range of pitching rotation timing, delayed rotation requires less aerodynamic power than the symmetric rotation. As for the horizontal force, delayed rotation with low αmd and high αmu is recommended for long-duration flight owing to its high efficiency, and advanced rotation should be employed for hovering flight for nearly zero horizontal force. The present study suggests that manipulating the angle of attack during a flapping cycle is the most effective way to control the aerodynamic forces and corresponding power expenditure for a dragonfly-like inclined flapping wing.

Operation of the alula as an indicator of gear change in hoverflies

The alula is a hinged flap found at the base of the wings of most brachyceran Diptera. The alula accounts for up to 10 per cent of the total wing area in hoverflies (Syrphidae), and its hinged arrangement allows the wings to be swept back over the thorax and abdomen at rest. The alula is actuated via the third axillary sclerite, which is a component of the wing hinge that is involved in wing retraction and control. The third axillary sclerite has also been implicated in the gear change mechanism of flies. This mechanism allows rapid switching between different modes of wing kinematics, by imposing or removing contact with a mechanical stop limiting movement of the wing during the lower half of the downstroke. The alula operates in two distinct states during flight-flipped or flat-and we hypothesize that its state indicates switching between different flight modes. We used high-speed digital video of free-flying hoverflies (Eristalis tenax and Eristalis pertinax) to investigate whether flipping of the alula was associated with changes in wing and body kinematics. We found that alula state was associated with different distributions of multiple wing kinematic parameters, including stroke amplitude, stroke deviation angle, downstroke angle of incidence and timing of supination. Changes in all of these parameters have previously been linked to gear change in flies. Symmetric flipping of the alulae was associated with changes in the symmetric linear acceleration of the body, while asymmetric flipping of the alulae was associated with asymmetric angular acceleration of the body. We conclude that the wings produce less aerodynamic force when the alula is flipped, largely as a result of the accompanying changes in wing kinematics. The alula changes state at mid-downstroke, which is the point at which the gear change mechanism is known to come into effect. This transition is accompanied by changes in the other wing kinematic parameters. We therefore find that the state of the alula is linked to the same parameters as are affected by the gear change mechanism. We conclude that the state of the alula does indeed indicate the operation of different flight modes in Eristalis, and infer that a likely mechanism for these changes in flight mode is the gear change mechanism.

Deformable wing kinematics in free-flying hoverflies.

Here, we present a detailed analysis of the deforming wing kinematics of free-flying hoverflies (Eristalis tenax, Linnaeus) during hovering flight. We used four high-speed digital video cameras to reconstruct the motion of approximately 22 points on each wing using photogrammetric techniques. While the root-flapping motion of the wing is similar in both the downstroke and upstroke, and is well modelled as a simple harmonic motion, other wing kinematic parameters show substantial variation between the downstroke and upstroke. Whereas the magnitude of the angle of incidence varies considerably within and between different hoverflies, the twist distribution along the wing is highly stereotyped. The angle of incidence and camber both show a recoil effect as they change abruptly at stroke reversal. Pronation occurs consistently after stroke reversal, which is perhaps surprising, because this has been found to reduce lift production in modelling studies. We find that the alula, a hinged flap near the base of the wing, operates in two discrete states: either in plane with the wing, or flipped approximately normal to it. We hypothesize that the alula may be acting as a flow-control device.

Control of flight forces and moments by flapping wings of model bumblebee

The control of flight forces and moments by flapping wings of a model bumblebee is studied using the method of computational fluid dynamics. Hovering flight is taken as the reference flight: Wing kinematic parameters are varied with respect to their values at hovering flight. Moments about (and forces along) x, y, z axes that pass the center of mass are computed. Changing stroke amplitude (or wingbeat frequency) mainly produces a vertical force. Changing mean stroke angle mainly produces a pitch moment. Changing wing angle of attack, when down-and upstrokes have equal change, mainly produces a vertical force, while when down-and upstrokes have opposite changes, mainly produces a horizontal force and a pitch moment. Changing wing rotation timing, when dorsal and ventral rotations have the same timing, mainly produces a vertical force, while when dorsal and ventral rotations have opposite timings, mainly produces a pitch moment and a horizontal force. Changing rotation duration has very small effect on forces and moments. Anti-symmetrically changing stroke amplitude (or wingbeat frequency) of the contralateral wings mainly produces a roll moment. Anti-symmetrically changing angles of attack of the contralateral wings, when down-and upstrokes have equal change, mainly produces a roll moment, while when down-and upstrokes have opposite changes, mainly produces a yaw moment. Anti-symmetrically changing wing rotation timing of the contralateral wings, when dorsal and ventral rotations have the same timing, mainly produces a roll moment and a side force, while when dorsal and ventral rotations have opposite timings, mainly produces a yaw moment. Vertical force and moments about the three axes can be separately controlled by separate kinematic variables. A very fast rotation can be achieved with moderate changes in wing kinematics.