Acoustically actuated miniature underwater robot with frequency-controlled multi-DOF locomotion

Abstract Existing underwater robot propulsion typically relies on disturbance of fluid generated via moving structures, such as propellers and biomimetic systems. However, in narrow and confined scenarios, e.g. coral reef crevices and pipelines, limited maneuvering space and complex aquatic environments containing floating particles may cause entanglement and blockage issues of actuators, imposing requirements for miniature underwater robot with high agility. This paper proposes a multi-degree-of-freedom actuation method for miniature underwater robot, which is driven using acoustic radiation force generated by compact piezoelectric transducers without any moving structures. Multiple actuators are connected in parallel, then selected and activated through frequency manipulation to achieve maneuverable locomotion. With a body length of 6 cm, the miniature underwater robot achieves a maximum straight-line velocity of 10.05 cm s ⁻¹ and a maximum angular velocity of 32.4 deg s ⁻¹ . The proposed miniature robot brings new insight for agile locomotion of miniature underwater robots, and a micro camera is carried for obstacle avoidance, demonstrating its application prospect in exploration of narrow underwater environments.