Hydraulic Volumetric Soft Everting Vine Robot Steering Mechanism for Underwater Exploration

Abstract

Despite a significant proportion of the Earth being covered in water, exploration of what lies below has been limited due to the challenges and difficulties inherent in the process. Current state of the art robots such as Remotely Operated Vehicles (ROVs) and Autonomous Underwater Vehicles (AUVs) are bulky, rigid and unable to conform to their environment. Soft robotics offers solutions to this issue. Fluid-actuated eversion or growing robots, in particular, are a good example. While current eversion robots have found many applications on land, their inherent properties make them particularly well suited to underwater environments. An important factor when considering underwater eversion robots is the establishment of a suitable steering mechanism that can enable the robot to change direction as required. This project proposes a design for an eversion robot that is capable of steering while underwater, through the use of bending pouches, a design commonly seen in the literature on land-based eversion robots. These bending pouches contract to enable directional change. Similar to their land-based counterparts, the underwater eversion robot uses the same fluid in the medium it operates in to achieve extension and bending but also to additionally aid in neutral buoyancy. The actuation method of bending pouches meant that robots needed to fully extend before steering was possible. Three robots, with the same design and dimensions were constructed from polyethylene tubes and tested. Our research shows that although the soft eversion robot design in this paper was not capable of consistently generating the same amounts of bending for the inflation volume, it still achieved suitable bending at a range of inflation volumes and was observed to bend to a maximum angle of 68 degrees at 2000 ml, which is in line with the bending angles reported for land-based eversion robots in the literature.

Figures (7)

• Figure 1: Side view of robot
• Figure 2: (Left) Top view of robot in retracted state showing the extension movement that it is capable of producing in this state. (Right) Top view of robot in everted state showing the bending movements that it is capable of (black arrows and text) and the 4 main parts that make up the robot (green arrows and text).
• Figure 3: Construction of the fixed robot base
• Figure 4: (a) The assembly of the everting section of the robot from three polyethylene tubes and the position of the balloon glue in relation to the bending pouches. (b) This figure shows the assembled eversion robot with its base and the dimensions of the bending pouches.
• Figure 5: Experimental setup to obtain bending angles based on volume of water.