Internal Seminar Series 2011, 2011-03-16
C18, 15:00
School of MACE, The University of Manchester



Simulating an Insect-Scale Flapping Wing Air Vehicle

Ben Parslew

  ben.parslew-2@postgrad.manchester.ac.uk  

Files: Abstract: pdf Presentation: ppt

Abstract



Interest in the development of flapping wing air vehicles has prompted a significant amount of research on the kinematics and aerodynamics of flapping flight in nature. Subsequently, several studies have considered how vehicle designs could mimic the function or form of flying organisms (Figure 1). At insect scale, success has been achieved in developing a micro air vehicle using sophisticated methods of manufacture (Wood, 2008). However, there is still potential to explore non biomimetic designs, which may offer benefits in terms of manufacturing cost and flight performance.

Figure 1: Examples of biomimetic designs of insect-scale flapping-wing air vehicles from Wood (2008) and Deng et al. (2006)

Recently, a flapping wing vehicle was developed that does not aim to replicate the structure or wingbeat kinematics of an insect (Figure 2). This design is a new class of vehicle that utilises a hingeless power transmission system. Strain from a piezoelectric transducer (PZT) is amplified using a flexible, folded cantilever arm, resulting in large displacements of the wing. This transmission system is dissimilar in form to those found in insects.

Figure 2: A flapping wing air vehicle designed with a hingeless transmission system.

Method

The modelling philosophy of the present work is to develop a parsimonious theoretical model of the hingeless flapping wing air vehicle that is useful for preliminary design. Strategic modelling is required to maintain a suitable level of accuracy without incurring excessive computational cost. Therefore the present work draws largely upon methods used in the preliminary analysis of aircraft aeroelasticity, to construct a robust discrete element model that is representative of the fundamental system dynamics. The process of system identification is used to construct a discrete element model of the vehicle wing and transmission system using finite element simulation results and experimental data (Figure 3).

Figure 3: Transmission system geometry used for finite element model (a); experimental apparatus used for step response tests (b); discrete element models with quadratic, binary wing, and elastic wing aerodynamic models(c).

The equations of motion governing the discrete element models were solved numerically to determine the time histories of driver plate displacement, y1(t), arm displacement, y2,(t) and wing displacement, θ3(t), for varying amplitudes and frequencies of driver signal, F1(t). In addition, the mean aerodynamic thrust, T3, was predicted using blade-element theory.

Results

The thrust time histories show that the elastic wing model is capable of achieving a greater peak thrust than the binary model (Figure 4 (b)). This is due to the increased drag in the binary model resulting in lower arm and wingbeat velocities, and hence reduced aerodynamic forces. However, despite having a smaller peak thrust, the binary wing model generates a greater net thrust, due to the wing remaining oriented at an angle that yields maximum lift throughout the wingbeat. Similar results are seen for all frequencies and amplitudes of forcing function (Figure 1 (c)).

Figure 4: Wing displacement (a) and thrust (b) time histories at the system resonant frequency for the binary and elastic wing aerodynamic models; variation in thrust with forcing signal frequency (c) for binary and elastic wing aerodynamic models.

References

  1. Wood, R. (2008). The first takeoff of a biologically inspired at-scale robotic insect. IEEE Transactions on Robotics 24(2), 341-347.
  2. Deng, X., Schenato, L., Wu, W., and Sastry, S. (2006). Flapping flight for biomimetic robotic insects: part I-system modeling. IEEE Transactions on Robotics, 22(4), 776-788.


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