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.