Department of Physiology, Development and Neuroscience, University of Cambridge, Downing Street, Cambridge CB3 2EG, UK.
Department of Ecology, Evolution, and Behavior, University of Minnesota, Saint Paul, MN 55108, USA.
J R Soc Interface. 2018 Oct 17;15(147):20180466. doi: 10.1098/rsif.2018.0466.
When aiming to capture a fast-moving target, animals can follow it until they catch up, or try to intercept it. In principle, interception is the more complicated strategy, but also more energy efficient. To study whether simple feedback controllers can explain interception behaviours by animals with miniature brains, we have reconstructed and studied the predatory flights of the robber fly and killer fly Although both species catch other aerial arthropods out of the air, contrasts prey against the open sky, while hunts against clutter and at much closer range. Thus, their solutions to this target catching task may differ significantly. We reconstructed in three dimensions the flight trajectories of these two species and those of the presented targets they were attempting to intercept. We then tested their recorded performances against simulations. We found that both species intercept targets on near time-optimal courses. To investigate the guidance laws that could underlie this behaviour, we tested three alternative control systems (pure pursuit, deviated pursuit and proportional navigation). Only proportional navigation explains the timing and magnitude of fly steering responses, but with differing gain constants and delays for each fly species. uses a dimensionless navigational constant of ≈ 3 with a time delay of ≈28 ms to intercept targets over a comparatively long range. This constant is optimal, as it minimizes the control effort required to hit the target. In contrast, uses a constant of ≈ 1.5 with a time delay of ≈18 ms, this setting may allow to cope with the extremely high line-of-sight rotation rates, which are due to close target proximity, and thus prevent overcompensation of steering. This is the first clear evidence of interception supported by proportional navigation in insects. This work also demonstrates how by setting different gains and delays, the same simple feedback controller can yield the necessary performance in two different environments.
当动物试图捕捉快速移动的目标时，它们可以选择跟踪目标直至追上，或者尝试拦截目标。原则上，拦截是更复杂的策略，但也更节能。为了研究具有微型大脑的动物是否可以通过简单的反馈控制器来解释拦截行为，我们重建并研究了强盗蝇和盗蝇的捕食飞行 。虽然这两个物种都是从空中捕捉其他空中节肢动物，但 将猎物与开阔的天空作对比，而 在更接近的范围内与杂物作对比。因此，它们解决这个目标捕捉任务的方法可能有很大的不同。我们以三维的形式重建了这两个物种的飞行轨迹，以及它们试图拦截的目标的飞行轨迹。然后，我们将它们的记录性能与模拟进行了对比测试。我们发现这两个物种都以近乎最优的时间捕获目标。为了研究可能存在的制导规律，我们测试了三种替代控制系统（纯追踪、偏离追踪和比例导航）。只有比例导航可以解释苍蝇转向反应的时间和幅度，但对于每种苍蝇物种，其增益常数和延迟都不同。 使用无量纲导航常数 ≈3 且延迟 ≈28 ms 来拦截比较长距离的目标。该常数是最优的，因为它可以最小化击中目标所需的控制努力。相比之下， 使用常数 ≈1.5 且延迟 ≈18 ms，这种设置可能允许 应对极高的视线旋转率，这是由于接近目标所致，从而防止转向过度补偿。这是昆虫中比例导航支持的首次明确的拦截证据。这项工作还表明，通过设置不同的增益和延迟，相同的简单反馈控制器可以在两种不同的环境中产生必要的性能。
