Abstract: The telescopic in-pipe robot based on the cam self-locked principle is developed to increase the pull of telescopic robots applied in the pipeline inspection. Its pull is beyond the limit of a constant friction, and can always increase with the engineering requirement if the power permits. A set of design method is worked out, including the relationship among parameters of the unilateral locker mechanism, the profile of the cam which can adapt to pipe diameter variation automatically, and the responding time of the locomotive system. A prototype based on the method is developed, and its performance experiments are presented. The research results help to improve the adaptability and pull ability, and perfect the design theory of telescopic in-pipe robots based on self-locked principle.

Key words: Pipeline diameter variation, Pull, Self-locked principle, Telescopic in-pipe robot, Micro contact surface Contact stress Shear stress Polyether-ether-ketone Seawater radial piston pump