Liu and Sun.pdf

2014 INTRODUCTION To understand the aerodynamics, energetics and control of insect flight, it is necessary to know the time history of the aerodynamic forces and moments produced by the flapping wings. It is difficult, even impossible, to directly measure the forces and moments on the wings of a freely flying insect. Existing means of circumventing this limitation are to measure experimentally or to compute numerically the forces and moments on model insect wings (e.g. Dickinson et al., 1999; Usherwood and Ellington, 2002a; Usherwood and Ellington, 2002b; Sun and Tang, 2002a). In order to use the experimental and computational methods to obtain the aerodynamic forces and moments and to study insect flight, measurements of wing kinematics and some morphological parameters are required. Other researchers have measured wing kinematics of many insects in free flight, using high-speed cine or video; and also measured morphological data of these insects (Ellington, 1984a; Ellington, 1984b; Dudley and Ellington, 1990; Willmott and Ellington, 1997). But since these reported studies used only one camera, the continuous time variation of wing orientation (geometrical angle of attack, wing rotation rate, etc.) could not be obtained. Recently, the time course of three-dimensional (3D) wing motion of freely flying fruit flies was measured using three orthogonally aligned, high-speed cameras (Fry et al., 2005). Measurements of 3D wing motion of other insects are of great interest, but some limitations to Fry et al.’s work meant that morphological parameters such as weight and position of center of mass could not be measured. If these data were also measured, one could use them to test the experimental and computational models (a reasonable test of the experimental and computational models is that the measured or computed vertical force approximately balances the insect weight and, in hovering flight, the horizontal force and the pitching moment about the centre of mass of the ins