Harvard University, John A. Paulson School of Engineering and Applied Sciences, Cambridge, MA 02138, United States of America.
Department of Organismal and Evolutionary Biology, Harvard University, Cambridge, MA 02138, United States of America.
Bioinspir Biomim. 2021 Feb 10;16(2). doi: 10.1088/1748-3190/abd013.
Fish migrate across considerable distances and exhibit remarkable agility to avoid predators and feed. Fish swimming performance and maneuverability remain unparalleled when compared to robotic systems, partly because previous work has focused on robots and flapping foil systems that are either big and complex, or tethered to external actuators and power sources. By contrast, we present a robot-the Finbot-that combines high degrees of autonomy, maneuverability, and biomimicry with miniature size (160 cm). Thus, it is well-suited for controlled three-dimensional experiments on fish swimming in confined laboratory test beds. Finbot uses four independently controllable fins and sensory feedback for precise closed-loop underwater locomotion. Different caudal fins can be attached magnetically to reconfigure Finbot for swimming at top speed (122 mm s≡ 1 BL s) or minimal cost of transport (CoT = 8.2) at Strouhal numbers as low as 0.53. We conducted more than 150 experiments with 12 different caudal fins to measure three key characteristics of swimming fish: (i) linear speed-frequency relationships, (ii) U-shaped CoT, and (iii) reverse Kármán wakes (visualized with particle image velocimetry). More fish-like wakes appeared where the CoT was low. By replicating autonomous multi-fin fish-like swimming, Finbot narrows the gap between fish and fish-like robots and can address open questions in aquatic locomotion, such as optimized propulsion for new fish robots, or the hydrodynamic principles governing the energy savings in fish schools.
鱼类可以迁移相当长的距离，并表现出非凡的敏捷性来躲避捕食者和觅食。鱼类的游泳性能和机动性仍然是机器人系统无与伦比的，部分原因是之前的工作主要集中在机器人和扑翼式水翼系统上，这些系统要么体积庞大且复杂，要么需要与外部执行器和电源连接。相比之下，我们提出了一种名为 Finbot 的机器人，它结合了高度自主性、机动性和仿生学，同时体积小巧（160 厘米）。因此，它非常适合在受限的实验室试验床上对鱼类进行受控的三维游泳实验。Finbot 使用四个独立控制的鳍和传感器反馈来实现精确的闭环水下运动。不同的尾鳍可以通过磁性附着来重新配置 Finbot，以实现最高速度（122 毫米每秒≡ 1 BL 秒）或最低运输成本（CoT = 8.2）的游泳，斯特劳哈尔数低至 0.53。我们进行了超过 150 次实验，使用了 12 种不同的尾鳍，以测量游泳鱼类的三个关键特性：（i）线性速度-频率关系，（ii）U 形 CoT，以及（iii）反向卡门涡（用粒子图像测速法可视化）。CoT 较低的地方出现了更像鱼的尾流。通过复制自主的多鳍鱼式游泳，Finbot 缩小了鱼类和类鱼机器人之间的差距，并可以解决水生运动中的一些开放性问题，例如为新的鱼类机器人优化推进，或鱼类群体中节约能量的水动力原理。
