Abstract: “In-pipe robotic systems are increasingly being used for visual inspection and nondestructive testing to monitor block, corrosion, crack, defect, and wall thickness of pipeline networks. In this paper an in-pipe mobile robot with the passive ability of adaptation to pipe diameter is presented. Its mechanical structure consists of three sets of parallelogram wheeled leg mechanism which are circumferentially spaced out 120 degrees apart symmetrically. Using a simple preloaded spring makes this structural design capable to realize the adaptation to a wide range of pipe diameters, from 20 to 32 inch, and also wheel normal forces adjustment. On the basis of analyzing the mechanical actions of the adaptation to pipe diameter and normal force adjusting, the related mechanical models are derived. Using simulations performed by Msc Adams the derived models are validated and also the ability of robot in performing challenging tasks in different pipe profiles is inspected. Dynamic simulations prov”

Keywords: in-pipe robot, passive pipe diameter adaptability, normal force adjusting, pipelines inspection