Design and Experimental Validation of a Worm-Like Tensegrity Robot for In-Pipe Locomotion

Traditional rigid-body in-pipe robots usually have complex and heavy structures with limited flexibility and adaptability. Although soft in-pipe robots have great improvements in flexibility, they still have manufacturing difficulties due to their reliance on high-performance soft materials. Tensegrity structure is a kind of self-stressed spatial structure consisting discrete rigid struts connected by a continuous net of tensional flexible strings, which combines the advantages of both rigid structures and soft structures. By applying tensegrity structures into robotics, this paper proposes a novel worm-like tensegrity robot for moving inside pipes. First, a robot module capable of body deformation is designed based on the concept of tensegrity and its deformation performance is analyzed. Then, the optimal parameters of the module are obtained based on the tensegrity form-finding. The deformation ability of the tensegrity module is tested experimentally. Finally, the worm-like tensegrity robot that can crawl inside pipes is developed by connecting three modules in series. Motion performance and load capacity are tested on the prototype of the worm-like tensegrity robot by experiments of moving in horizontal pipe, vertical pipe, and elbow pipe. Experimental results demonstrate the effectiveness of the proposed design and suggest that the robot has high compliance, mobility, and adaptability although with simple structure and low cost.