Single-Actuator Robotic Grinding System with Planetary Gear Coupling for Rust Removal on Pipe Outer Surfaces

Rust removal on pipe surfaces is hazardous and labor-intensive, yet it is a prerequisite for inspection and recoating in maintenance. Existing solutions rely on industrial robots or specialized robots with limited obstacle-negotiation capability and cable entanglement risks. This work presents a Robotic Pipe Grinding System (RPGS) for straight pipes and focuses on the latest generation, RPGS-III. Driven by a single motor, RPGS-III integrates cutter self-rotation, revolution about the pipe axis, and axial translation through planetary-gear and bevel-gear transmissions. Passive mechanisms enable adaptation to different pipe diameters, obstacle negotiation, and dust containment during grinding. Kinematic and static analyses, motion simulations, and prototype experiments were conducted to validate the system, with feasibility demonstrated through in situ maintenance tests. The validated design demonstrates a practical solution for automated pipe maintenance in field environments, reducing actuation complexity while maintaining operational effectiveness.