Design and Experimental Verification of a Hybrid Locomotion-Clamping Module for Pipes with Varying Diameters

This paper presents a key module of a newly proposed low-cost in-pipe inspection robot (IPIR) designed for aging pipeline infrastructure with varying diameters and complex geometries, including T-junctions. Conventional IPIRs, typically optimized for pipes with fixed diameters, exhibit limited performance in such environments. To address this limitation, a module enabling hybrid control of travel speed and clamping force for posture stabilization is introduced. The proposed module employs a two-link end-point drive mechanism, incorporating active wheels at the link ends and passive wheels at the joint. End-point wheel actuation regulates joint angles and movement velocity, while differential motor torque generates the required clamping force at the joint. Experimental results demonstrate stable operation and effective adaptation to a wide range of pipe diameters without the use of force sensors. Eliminating force sensors reduces system cost and structural complexity. Despite its simple structure, the module autonomously accommodates diverse pipe diameters using the link mechanism. These features support the development of a scalable IPIR platform capable of navigating complex and aging pipeline networks.