Design of an In-Pipe Robot with Contact-Angle-Guided Kinematic Decoupling for Crosstalk-Suppressed Locomotion

2026-03-28

AI Summary

This study addresses the challenge of performance interference between posture adjustment and propulsion in pipe robots navigating complex three-dimensional pipelines, caused by motion coupling. To resolve this, the authors propose a V-shaped robot architecture that physically decouples rolling and propulsion through a separated layout of joint axes and wheel mechanisms, enabling full-wheel drive and active roll control with only two motors. A novel contact-angle-guided kinematic decoupling mechanism is introduced, supported by a drive transmission matrix and geometric transmission model, which reveals the contact angle as the critical parameter for suppressing cross-coupling effects. Based on this insight, design guidelines for structural optimization are established. Experimental validation demonstrates nearly constant propulsion torque during rolling maneuvers and 100% success over more than ten round-trip traversals through multi-material pipelines containing double bends.

Abstract

In-pipe inspection robots must traverse confined pipeline networks with elbows and three-dimensional fittings, requiring both reliable axial traction and rapid rolling reorientation for posture correction. In compact V-shaped platforms, these functions often rely on shared contacts or indirect actuation, which introduces strong kinematic coupling and makes performance sensitive to geometry and friction variations. This paper presents a V-shaped in-pipe robot with a joint-axis-and-wheel-separation layout that provides two physically independent actuation channels, with all-wheel-drive propulsion and motorized rolling reorientation while using only two motors. To make the decoupling mechanism explicit and designable, we formulate an actuation transmission matrix and identify the spherical-wheel contact angle as the key geometric variable governing the dominant roll-to-propulsion leakage and roll-channel efficiency. A geometric transmission analysis maps mounting parameters to the contact angle, leakage, and efficiency, yielding a structural guideline for suppressing crosstalk by driving the contact angle toward zero. A static stability model further provides a stability-domain map for selecting torsion-spring stiffness under friction uncertainty to ensure vertical-pipe stability with a margin. Experiments validate the decoupling effect, where during high-dynamic rolling in a vertical pipe, the propulsion torque remains nearly invariant. On a multi-material testbed including out-of-plane double elbows, the robot achieved a 100% success rate in more than 10 independent round-trip trials.

Problem

• in-pipe robot
• kinematic coupling
• crosstalk
• locomotion
• contact angle

Innovation

• kinematic decoupling
• contact angle
• in-pipe robot
• crosstalk suppression
• actuation transmission matrix