Improvement of a Screw Drive In-Pipe Robot with Pathway Selection Mechanism to Pass Through T-Branches

This paper discusses the improvement of a screw drive in-pipe robot with a pathway selection mechanism. This robot is composed of three units: a screw driving unit called a rotator unit (front unit), a steering unit that bends the front unit (middle unit), and a stator unit to hold the whole body (rear unit). It passes not only through straight pipes but also bent pipes and T-branches by changing driving modes (screw driving mode, steering mode and rolling mode). These modes are performed by just two motors through a differential mechanism. The screw drive in-pipe robot previously developed cannot pass through certain T-branches. In this paper, the rear unit has been improved to solve this problem. Constraints on robot length in T-branches caused by this improvement are discussed, that is, installation of additional passive wheels on the rear unit and its rectangle model in the T-branch. Finally, to verify the effect of this improvement and its mobility, experiments are conducted in straight, bent and T-branch pipes.