An Underwater Jet-Propulsion Soft Robot with High Flexibility Driven by Water Hydraulics

Compared with rigid robots, soft robots have the advantages of inherent compliance, high adaptability, and impact tolerance. Many researchers are very interested in the motion design of soft robot underwater. In this paper, inspired by the method of octopus propulsion, a jet propulsion unit with 80% soft materials driven by pressure is designed. It can change the volume of its cavity to absorb and eject the fluid medium to make the robot move. According to the working characteristics of the jet unit, corresponding experiments are designed to analyze its force output, deformation, ejection flow, and pressure response characteristics. In order to expand the motion space of the robot, a buoyancy unit is designed to control the depth of the robot in the water. Three jet units and a buoyancy element are combined into a tetrahedron robot - jet soft robot (JSR). The feasibility of its motion is verified by experiments. Compared with other similar jet robots, the biggest feature of this robot is that the drive unit can bend or twist roughly along the centerline, which can prevent accidental collision and damage.