Passive Underwater Robot Hand Utilizing Water Resistance

Numerous robot grippers have been developed to reduce energy consumption by utilizing contact forces with fixed objects. In underwater environments, most objects are not fixed, particularly in the mid and surface layers, posing a challenge for obtaining contact forces. To address this issue, this study proposes a multi-finger gripper that utilizes water resistance for opening and closing actions underwater. As the gripper ascends in water, it closes its fingers, each equipped with a locking mechanism at the tip. This mechanism allows the fingers to maintain a closed shape when converged towards the center and locked. Unlocking occurs when the gripper descends underwater, as the direction of water resistance changes. This design enables locking and unlocking without actuators, offering a solution for grasping underwater objects. The gripper’s underwater movement has speed limits. Below the lower limit, fingers may not achieve sufficient bending, while exceeding the upper limit can cause vibrations and affect the locking function. Therefore, maintaining an appropriate speed is crucial. Finally, gripping experiments were conducted to confirm the gripper’s ability to grasp objects underwater.