Fish exhibit impressive locomotive performance and agility in complex underwater environments, using their undulating tails and pectoral fins for propulsion and maneuverability. Replicating these abilities in robotic fish is challenging; existing designs focus on either fast swimming or directional control at limited speeds, mainly within a confined environment. To address these limitations, we designed Snapp, an integrated robotic fish capable of swimming in open water with high speeds and full 3-dimensional maneuverability. A novel cyclic-differential method is layered on the mechanism. It integrates propulsion and yaw-steering for fast course corrections. Two independent pectoral fins provide pitch and roll control. We evaluated Snapp in open water environments. We demonstrated significant improvements in speed and maneuverability, achieving swimming speeds of 1.5 m/s (1.7 Body Lengths per second) and performing complex maneuvers, such as a figure-8 and S-shape trajectory. Instantaneous yaw changes of 15$^{\circ}$ in 0.4 s, a minimum turn radius of 0.85 m, and maximum pitch and roll rates of 3.5 rad/s and 1 rad/s, respectively, were recorded. Our results suggest that Snapp's swimming capabilities have excellent practical prospects for open seas and contribute significantly to developing agile robotic fishes.

翻译：鱼类利用其摆动尾部和胸鳍进行推进与机动，在复杂水下环境中展现出卓越的运动性能与敏捷性。在仿生机器鱼中复现这些能力极具挑战性——现有设计或聚焦于快速游动，或局限于有限速度下的定向控制，且主要在受限环境中运行。为突破这些局限，我们设计了集成化仿生机器鱼Snapp，使其能在开放水域实现高速游动与全三维机动。一种新颖的循环差分方法被分层集成至机械结构中，该方法融合了推进与偏航转向控制以实现快速航向修正。两个独立胸鳍提供俯仰与滚转控制。我们在开放水域环境中对Snapp进行了评估，实验表明其在速度与机动性方面取得显著提升：游动速度达1.5米/秒（1.7倍体长/秒），可完成8字形与S形轨迹等复杂机动。记录到瞬时偏航变化率15°/0.4秒、最小转弯半径0.85米、最大俯仰角速度3.5弧度/秒及最大滚转角速度1弧度/秒的性能指标。研究结果表明，Snapp的游动能力在公海领域具有优异的应用前景，并显著推动了敏捷仿生机器鱼的发展。