Gotta catch 'em all, safely! Aerial-deployed soft underwater gripper

Abstract

Underwater soft grippers exhibit potential for applications such as monitoring, research, and object retrieval. However, existing underwater gripping techniques frequently cause disturbances to ecosystems. In response to this challenge, we present a novel underwater gripping framework comprising a lightweight gripper affixed to a custom submarine pod deployable via drone. This approach minimizes water disturbance and enables efficient navigation to target areas, enhancing overall mission effectiveness. The pod allows for underwater motion and is characterized by four degrees of freedom. It is provided with a custom buoyancy system, two water pumps for differential thrust and two for pitching. The system allows for buoyancy adjustments up to a depth of 6 meters, as well as motion in the plane. The 3-fingered gripper is manufactured out of silicone and was successfully tested on objects with different shapes and sizes, demonstrating a maximum pulling force of up to 8 N when underwater. The reliability of the submarine pod was tested in a water tank by tracking its attitude and energy consumption during grasping maneuvers. The system also accomplished a successful mission in a lake, where it was deployed on a hexacopter. Overall, the integration of this system expands the operational capabilities of underwater grasping, makes grasping missions more efficient and easy to automate, as well as causing less disturbance to the water ecosystem.

Figures (10)

• Figure 1: Outdoor tests on a lake in Switzerland. The system composed of the pod (yellow) and the gripper (white) is grasping a 3D-printed-crab while suspended on a hexacopter.
• Figure 2: A) Pod-gripper system design. B) Casting mold for the gripper and C) pod. For the case of the pod, outer-shell (blue) inner-shell (red) and base-plate (green).
• Figure 3: Calculated actuation-Force and Volume of the pod while actuating the buoy servo system at a constant water depth of 0.5m.
• Figure 4: Electronics' scheme.
• Figure 5: A) Von Mises stress analysis due to 0,1 MPa of pressure. B) Gripper grasping a sphere underwater while the latter is pulled upwards. Stress analysis according to von Mises method. C) Deformation of the soft skin at a depth of, respectively, 0.5m (a) and 1.5m (b). Number of elements: 6279. Element type: Solid187.