Directing Anisotropic Friction and Compliant Structures Towards In-pipe Locomotion & Navigation

In-pipe locomotion is a great proving ground for the environmental flexibilities of soft robots. The 2023 Robosoft conference locomotion competition captured many of these chal-lenges and opportunities as a series of in-pipe obstacles for soft robots to navigate. Locomotion through pipes of different sizes, and surfaces, and navigating T-junctions was demonstrated. This paper presents the design of the competition-winning robot, using inchworm-inspired bellows actuated locomotion to move forward via anisotropic friction from the robot body design. The robot can traverse pipe diameters of 5cm to 10cm and can navigate T-junctions via a compliant guide rod that can be rotated to choose heading direction and cross over gaps in the pipeline. This paper also shows further development of the competition robot to generalise for more pipe designs by having the setae be a compliant four-bar linkage mechanism. The final design of the robot only requires one onboard motor to rotate the semi-passive guide rod for navigation and one pneumatic line for the bellows actuator, with the compliant seta design taking up minimal volume in the pipe compared to other wall-mounting inchworm solutions.