Experimental verification of analytical torques enabling a screw drive in-pipe robot to pass through bent pipes

This paper presents the relationship between spring stiffness and motor torque of a screw drive in-pipe robot that passes through a bent pipe. Their values are derived from a cross-sectional analysis of a bent pipe and a static analysis of the robot that rotates with repeating expansion and contraction of its diameter in that cross-sectional shape. To verify the validity of the analysis results, a simple and light screw drive in-pipe robot capable of moving through small pipes was developed, and experiments were performed to compare the experimentally measured torque with the analytical results.