A dual-mode underwater robot with non-contact adsorption ability: Design, mode switching and field applications

Abstract

This paper proposes an underwater dual-mode operating robot (UDOR) capable of both swimming and wall-climbing. The UDOR can achieve 6 degrees of freedom (DOF) movement in swimming mode, similar to a remotely operated vehicle (ROV), and 3 DOF locomotion in wall-climbing mode, utilizing propeller-driven Bernoulli adsorption devices (PBDs). Since PBDs are non-contact suction cups, the robot can locomote flexibly in all directions on the wall by virtue of its omnidirectional wheels. Compared to robots limited to wall-climbing operations, UDOR offers enhanced mobility on challenging wall surfaces by switching modes: when encountering unclimbable areas, UDOR desorbs itself from the wall, transitions to swimming mode to reach the next climbable surface,and then resumes wall-climbing mode to continue operations. A fuzzy PID controller is designed for UDOR’s wall locomotion, enabling trajectory tracking through passive wheels controlled by thrusters. Laboratory experiments demonstrated swimming velocities up to 1.5 m/s and stable wall-climbing capabilities. Field trials conducted at a reservoir dam and on a steel-hulled vessel validated the robot’s performance under real operating conditions with waves, currents, and varied surface materials. The results demonstrate UDOR’s suitability for operating missions on underwater structures composed of diverse materials and complex terrains.