A Rigid–Flexible Multimodal Robot for Versatile Manipulation in Pipe Environments

This article presents a rigid–flexible multimodal robot developed for locomotion and target acquisition in confined pipe environments with variable geometries. The robot features a multimodal cable-driven rigid–flexible manipulator capable of performing multiple tasks without end-effector replacement. The rigid–flexible coupling architecture enhances adaptability to narrow and unstructured spaces while reducing the number of required actuators. A catheter transmission device based on angled scissor linkages is proposed to maintain a compact coiling profile and ensure consistent tension transmission during cable actuation. Its performance is validated through modeling of cable and conduit motion using a Coulomb friction model. Furthermore, a decoupled actuation strategy is introduced to enable simplified control across multimodal operations. Experimental results confirm that the robot can reliably grasp rigid objects of various geometries, as well as soft, slippery, fragile, and irregular targets that are challenging for conventional tools. The results further demonstrate the effectiveness of the robotic system in both locomotion and target acquisition within complex pipe environments.