A Magnetically Actuated Miniature Robotic Fish with the Flexible Tail Fin

Bionic robotic fish are of great importance in marine resource exploration, military applications and industrial production. However, existing bionic robotic fish often use motor-driven multi-link systems, which are complex and bulky. They are unable to perform narrow underwater operations and industrial pipeline exploration. Therefore, the miniaturization and simplification of bionic robotic fish have become an important research direction for underwater bionic robotic fish. This work reports a miniature robotic fish with a flexible tail fin based on a magnetic actuator (MAGFLE). The flexible tail fin dynamics model of MAGFLE was established and analyzed by numerical simulation to obtain the highest frequency of flexible tail fin propulsion efficiency. A unique magnetic actuator was designed to enable the flexible tail fin to achieve multi-mode motion under magnetic actuation. Thanks to the absence of transmission mechanisms or joints, the design of MAGFLE is notably simplified, resulting in a compact form factor measuring 76 × 37 × 40 mm³ and weighing a mere 5.6 grams. It accelerates from a standstill and travels up to 181.05 mm s^-1, which only needs 10 s (approximately 2.4 body lengths per second). The results indicate that the magnetically driven MAGFLE with a flexible tail fin has the advantage of a miniature structure, fast movement, and low noise, which has great potential for application in reconnaissance or exploration missions.