A novel bio-inspired soft pipeline robot with variable stiffness for navigating inside complex pipelines

Oil and gas pipelines transport highly flammable and explosive substances, making leaks potentially catastrophic. Regular inspections are therefore critical to prevent such incidents. Pipeline robots provide a safer and more efficient alternative to human inspectors, especially in hazardous and monotonous environments. However, conventional rigid pipeline robots face significant challenges in navigating complex, small- to medium-diameter pipelines, particularly those carrying dangerous substances, due to their limited flexibility and adaptability. To overcome these limitations, soft pipeline robots have emerged as a promising solution, leveraging their inherent flexibility and adaptability to such conditions. Nevertheless, the high compliance of existing soft robots often results in difficulties maintaining posture, especially when navigating branches in intricate pipeline systems. Inspired by the inchworm’s locomotion, this study introduces two types of variable-stiffness soft actuators and a soft pipeline robot designed to traverse complex, small- to medium-diameter pipelines. These innovations address the challenges faced by existing soft robots in such environments. The variable-stiffness characteristics of the actuators are thoroughly analyzed, and precise motion control strategies are developed to enhance the robot’s performance in complex pipeline navigation. Extensive testing of the robot prototype was conducted to evaluate its stiffness and motion capabilities in challenging pipeline scenarios. Experimental results demonstrate that the proposed variable-stiffness soft pipeline robot significantly outperforms existing models in adaptability to complex pipelines, branch-crossing ability, and transitioning from smooth surfaces into pipes. The developed soft actuators and robots hold broad potential for applications such as oil and gas pipeline inspections, chemical vessel inspections, and medical endoscopy.