A universal strategy for visually guided landing
A universal strategy for visually guided landing
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DOI：
10.1073/pnas.1314311110
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发表时间：
2013-11-12
影响因子：
11.1
通讯作者：
Srinivasan, Mandyam V.
中科院分区：
文献类型：
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作者：
Baird, Emily;Boeddeker, Norbert;Srinivasan, Mandyam V.
着陆是飞行的一个具有挑战性的方面，因为为了安全着陆，着陆时速度必须降低到接近零的值。动物实现这一点的机制尚不清楚。当降落在水平表面上时，蜜蜂通过保持表面在降低高度时产生的前后图像运动（光流）的速率恒定来控制它们的速度。然而，随着倾斜度的增加，这种简单的光流模式变得越来越复杂。蜜蜂在不同方向的表面着陆时是如何控制速度的？为了回答这个问题，我们分析了蜜蜂降落在垂直表面上的轨迹，产生各种运动模式。我们发现，降落的蜜蜂通过保持图像的膨胀率恒定来控制它们的速度。然后，当表面产生的表观膨胀率被人为操纵时，我们通过分析着陆来严格测试和证实这一假设。该策略确保在接近表面时逐渐且自动地降低速度。然后，我们开发了这种策略的数学模型，并表明它可以有效地用于引导任何方向的表面，包括水平表面上的平稳着陆。这种引导着陆的生物学策略不需要知道到地面的距离或接近地面的速度。这种着陆策略的简单性和通用性表明，它很可能被其他飞行动物利用，并使其成为飞行机器人导航系统的理想选择。
Landing is a challenging aspect of flight because, to land safely, speed must be decreased to a value close to zero at touchdown. The mechanisms by which animals achieve this remain unclear. When landing on horizontal surfaces, honey bees control their speed by holding constant the rate of front-to-back image motion (optic flow) generated by the surface as they reduce altitude. As inclination increases, however, this simple pattern of optic flow becomes increasingly complex. How do honey bees control speed when landing on surfaces that have different orientations? To answer this, we analyze the trajectories of honey bees landing on a vertical surface that produces various patterns of motion. We find that landing honey bees control their speed by holding the rate of expansion of the image constant. We then test and confirm this hypothesis rigorously by analyzing landings when the apparent rate of expansion generated by the surface is manipulated artificially. This strategy ensures that speed is reduced, gradually and automatically, as the surface is approached. We then develop a mathematical model of this strategy and show that it can effectively be used to guide smooth landings on surfaces of any orientation, including horizontal surfaces. This biological strategy for guiding landings does not require knowledge about either the distance to the surface or the speed at which it is approached. The simplicity and generality of this landing strategy suggests that it is likely to be exploited by other flying animals and makes it ideal for implementation in the guidance systems of flying robots.