Development and Control of an Underwater Vehicle–Manipulator System Propelled by Flexible Flippers for Grasping Marine Organisms

Robots have the potential to assist and complement humans in the exploration of hostile environments. For example, underwater vehicle-manipulator systems (UVMSs) have been researched and applied in underwater operations. Motivated by the need for collecting marine organisms cultivated in shallow sea aquafarm, a light-weight and portable UVMS propelled by flexible flippers (named, F-UVMS), rather than typical propellers or jet-based propulsion systems, is investigated. To this end, integrative mechatronic design of F-UVMS is first presented, involving 6 flipper propulsors for generating thrust in a flapping way, a four-degree-of-freedom (4-DOF) arm for grasping, and a certain amount of onboard sensors for environment perception. A thrust-power measurement platform was established to evaluate thrust-power relationship for different sizes and stiffness of flippers. Meanwhile, the locomotion modalities of F-UVMS were analyzed. A framework based on nonlinear model predictive control (NMPC) method was implemented to govern autonomous tracking marine organisms. The capabilities of F-UVMS were validated through a series of experiments in laboratory pool and field missions in real sea conditions.