Ristroph Leif, Berman Gordon J, Bergou Attila J, Wang Z Jane, Cohen Itai
Department of Physics, Cornell University, Ithaca, NY 14853, USA.
J Exp Biol. 2009 May;212(Pt 9):1324-35. doi: 10.1242/jeb.025502.
Flying insects perform aerial maneuvers through slight manipulations of their wing motions. Because such manipulations in wing kinematics are subtle, a reliable method is needed to properly discern consistent kinematic strategies used by the insect from inconsistent variations and measurement error. Here, we introduce a novel automated method that accurately extracts full, 3D body and wing kinematics from high-resolution films of free-flying insects. This method combines visual hull reconstruction, principal components analysis, and geometric information about the insect to recover time series data of positions and orientations. The technique has small, well-characterized errors of under 3 pixels for positions and 5 deg. for orientations. To show its utility, we apply this motion tracking to the flight of fruit flies, Drosophila melanogaster. We find that fruit flies generate sideways forces during some maneuvers and that strong lateral acceleration is associated with differences between the left and right wing angles of attack. Remarkably, this asymmetry can be induced by simply altering the relative timing of flips between the right and left wings, and we observe that fruit flies employ timing differences as high as 10% of a wing beat period while accelerating sideways at 40% g.
飞行昆虫通过对翅膀运动进行细微操控来完成空中机动动作。由于翅膀运动学中的此类操控很微妙，因此需要一种可靠的方法，以便从不一致的变化和测量误差中正确识别昆虫所采用的一致运动学策略。在此，我们介绍一种新颖的自动化方法，该方法能从自由飞行昆虫的高分辨率影片中准确提取完整的三维身体和翅膀运动学信息。此方法结合了视觉外壳重建、主成分分析以及有关昆虫的几何信息，以恢复位置和方向的时间序列数据。该技术在位置方面的误差较小且特征明确，小于3像素，在方向方面的误差为5度。为展示其效用，我们将这种运动跟踪应用于果蝇（黑腹果蝇）的飞行。我们发现果蝇在某些机动动作中会产生侧向力，并且强烈的横向加速度与左右翼攻角的差异有关。值得注意的是，这种不对称性可以通过简单改变左右翼翻转的相对时间来诱发，并且我们观察到果蝇在以40%重力加速度侧向加速时，会采用高达一个翅膀拍动周期10%的时间差异。
