Towards efficient pipe maintenance: DeWaLoP in-pipe robot stability controller

This paper describes the stability controller of the DeWaLoP (Developing Water Loss Prevention) in-pipe robot. The robot´s objective is to redevelop the pipe joints of fresh water supply systems by crawling into water canals and applying a restoration material to repair the pipes. The robot´s structure consists of six wheeled-legs, three on the front separated 120° and three on the back in the same configuration, supporting the structure along the centre of the pipe. The robot, by maintaining its structure in the pipe´s centre, enables the cleaning and sealing tools to work properly by rotating around the inner circumference of the pipe, similar to a cylindrical robot, covering the entire 3D in-pipe space. Likewise, the tools may exert different forces while working, pushing or pulling the structure of the robot and moving it out of its centered position. Moreover, the pipes have maximum degree of pressure of 6 bar, meaning that the pipes can break if the forces are not balanced. Therefore, robot requires to be calibrated at the center of the pipe before the maintenance task is implemented and a dynamic controller is needed to maintain a proportional pressure on each of the robot´s wheeled-legs for balancing the robot when the tools system (cleaning and sealing systems) are working.