Two DOF underactuated swimming robot with high maneuverability and passive adaptability

Exploring unknown underwater environments containing high densities of obstacles is a significant challenge for swimming robots. Many swimming animals can adapt to complex underwater terrain and swim through the clutter with their maneuverability and compliant bodies. Upon that premise, we designed a bioinspired two DOF soft swimming robot with high maneuverability and passive adaptability to obstacles. This swimming robot mimics the compliant vertebrate structure of biological swimmers and, with just two actuators, can not only perform basic maneuvers like forwarding locomotion (19.35 cm/s) and yaw/pitch turning (44.09 deg/s), but can also perform a novel roll rotation maneuver (107.78 deg/s). Additionally, the flexible ‘vertebrate’ and foldable fins allow the passive mechanical adaptability required to pass through narrow passages or cluttered terrain. We studied the robot’s obstacle passing capabilities among several underwater obstacles, including narrow upright poles, planar orifice, linear channel, and a set of tunnels. Even without closed-loop control, the robot passed through each obstacle configuration relatively efficiently. Such high maneuverability and passive adaptability would greatly enhance swimming robot locomotion robustness in complex, cluttered environments.