Automatic in-pipe robot centering from 3D to 2D controller simplification

Abstract

After 50 years the connections between fresh water pipes (800–1200mm diameter) need to be repaired due to aging and dissolution of the filling material. Only in Vienna 3000km of pipes need to be improved, which requires a robotic solution. The main challenge is to accurately align the robot axis with the pipe axis to enable the rotary motion of the maintenance tool. The tool system for cleaning and sealing is mounted on the maintenance unit of the robot consisting of six wheeled-legs. These legs extend to the irregular cast-iron pipe and set the robot structure eccentric to the pipe's center. In order to center the maintenance unit, distance sensors on the legs allow to adapt to the noncircular shape of the pipe. Correcting the leg extension allows to obtain better positioning of the cleaning tool.