This paper studies the trajectory tracking problem of flapping-wing micro aerial vehicles &#x0028 FWMAVs &#x0029 in the longitudinal plane. First of all, the kinematics and dynamics of the FWMAV are established, wherein the aerodynamic force and torque generated by flapping wings and the tail wing are explicitly formulated with respect to the flapping frequency of the wings and the degree of tail wing inclination. To achieve autonomous tracking, an adaptive control scheme is proposed under the hierarchical framework. Specifically, a bounded position controller with hyperbolic tangent functions is designed to produce the desired aerodynamic force, and a pitch command is extracted from the designed position controller. Next, an adaptive attitude controller is designed to track the extracted pitch command, where a radial basis function neural network is introduced to approximate the unknown aerodynamic perturbation torque. Finally, the flapping frequency of the wings and the degree of tail wing inclination are calculated from the designed position and attitude controllers, respectively. In terms of Lyapunov&#x02BC s direct method, it is shown that the tracking errors are bounded and ultimately converge to a small neighborhood around the origin. Simulations are carried out to verify the effectiveness of the proposed control scheme.

Modeling and trajectory tracking control for flapping-wing micro aerial vehicles

The three-dimensional structure of the flow behind a heaving and pitching finite-span wing is investigated using dye flow visualization at a Reynolds number of 164. Phase-locked image sequences, which are obtained from two orthogonal views, are combined to create a set of composite images that give an overall sense of the three-dimensional structure of the flow. A model of the vortex system behind the wing is constructed from the image sequences. Variations of the Strouhal number, pitch amplitude and heave/pitch phase angle are qualitatively shown to affect the structure of the wake.

A visual study of the flow structures behind a heaving and pitching finite-span wing

A review on fluid dynamics of flapping foils

We study numerically the propulsive wakes produced by a flapping foil. Both pure pitching and pure heaving motions are considered, respectively, at a fixed Reynolds number of Re = 1700. As the major innovation of this paper, we find an interesting coincidence that the efficiency maximum agrees well with the 2D-3D transition boundary, by plotting the contours of propulsive efficiency in the frequency-amplitude parametric space and comparing to the transition boundaries. Although there is a lack of direct 3D simulations, it is reasonable to conjecture that the propulsive efficiency increases with Strouhal number until the wake transits from a 2D state to a 3D state. By comparing between the pure pitching motion and the pure heaving motion, we find that the 2D-3D transition occurs earlier for the pure heaving foil than that of the pure pitching foil. Consequently, the efficiency for the pure heaving foil peaks more closely to the wake deflection boundary than that of the pure pitching foil. Furthermore, sinc...

The correlation between wake transition and propulsive efficiency of a flapping foil: A numerical study

Energy harvesting performance and flow structure of an oscillating hydrofoil with finite span

Categorization of flow structures around a pitching and plunging airfoil

Power extraction from wind and water streams using flapping wings is known to be an alternative method to harvest renewable energy. The vortical flow structures around and in the wake of a NACA0012 airfoil oscillating with non-sinusoidal pitching and plunging motions are investigated using digital particle image velocimetry and compared with Navier–Stokes computations to give insight into the physics that determine the performance of an oscillating-wing power generator for a plunge amplitude of 1.05 chords, reduced frequency of 0.8, pitch amplitude of 73 deg, pivot points at quarter and mid-chords, phase angles of 90 and 110 deg, and stroke reversal times (ΔTR) of 0.1 (rapid reversal) to 0.5 (sinusoidal reversal) at a Reynolds number of Re=1100. As the airfoil rotation speed during pitch reversals is increased, vortex shedding occurs earlier with higher strength. As the phase angle by which the pitching motion leads the plunging motion is increased, the shed vortex convection distance is also increased. T...

Flow Structures Around an Oscillating-Wing Power Generator

Effect of unequal flapping frequencies on flow structures

Large scale spanwise periodic vortex gusts or single spanwise vortex impinging on a rectangular wing

This study is funded by the Scientific and Technological Research Council of Turkey (TUBITAK) Grant 214M385.

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Idil Fenercioglu

Papers

Categorization of flow structures around a pitching and plunging airfoil

Flow Structures Around an Oscillating-Wing Power Generator

Effect of unequal flapping frequencies on flow structures

Large scale spanwise periodic vortex gusts or single spanwise vortex impinging on a rectangular wing

Effect of phase angle on tandem flapping-wing power generation