Single-Actuated Camshaft Robot With Multiple Sequential Motions

Pipeline inspection in unknown environments is challenging for robots, and various in-pipe crawling robots have been developed in recent years to perform pipeline inspection. Most of these robots comprise multiple parts and require multiple actuators to realize the pipeline locomotion, resulting in complicated system composition and large energy consumption. In this paper, inspired by the crawling principles of earthworm locomotion, we propose a single-actuated camshaft robot that can realize multiple sequential motions for pipeline crawling. The proposed single-actuated camshaft robot contains one actuator and three parts: head anchoring, body elongation, and rear anchoring part. The multiple sequential motions of these three parts are realized based on the cam mechanisms. Umbrella-shaped elastic rubbers are circumferentially around the head and rear anchoring parts. Each part contains a cam bracket. The camshaft’s rotatory motion pushes the cam brackets to generate the axial translational motion, resulting in the umbrella-shaped elastic rubbers being expanded or contracted. The proposed camshaft robot’s expansion and contraction motion are sequentially realized by the phase deviation of the camshafts. First, the structures of the proposed robot are designed. Then, the cam curves are modeled, the expansion/contraction ratio of the rear/head anchoring part is calculated, the phase deviation of the camshafts is determined, and multiple sequential motions of the proposed robot are simulated. Finally, we fabricate the proposed camshaft robot and carry out crawling experiments in pipelines with different shapes and diameters.