Optimization design and experiment study on a water hydraulic flexible actuator integrating flexible inner skeleton and soft external skin used for underwater flexible gripper

A water hydraulic flexible gripper with three flexible actuators is proposed, which integrates a soft external skin and a flexible inner skeleton to enhance resistance against water pressure. To investigate the deformation characteristics of the water hydraulic flexible actuator, a mathematical model is established to describe the relationship between water pressure and actuator deformation. The effects of different materials, structural sizes, and inlet pressure are analyzed through simulation. A Kriging model is utilized to fit the simulation results, while a multi-island genetic algorithm is employed to obtain an optimal solution for the structure of the flexible actuator. Finally, the deformation of the flexible actuator under various inlet pressures is quantified through experimental measurements, and the obtained results exhibit degree of consistency with the simulation outcomes. After completing static experiments at a simulated sea depth of 1000 m, the tip forces of flexible actuators were tested, and then land and underwater grasping experiments were conducted. The water-hydraulic flexible actuator developed in this study has great potential for handling fragile or deformable objects during deep-sea. This promotes the application of water-hydraulic flexible manipulators in the field of underwater robotics, providing higher flexibility and adaptability compared to traditional rigid manipulators.