Design and analysis of a rigid-flexible coupled earthworm-like robot

This paper presents a rigid-flexible coupled pipeline robot inspired by earthworms. The robot is composed of a single module equipped with a parallel crank-rocker mechanism for rigid radial expansion, steel wire ropes for axial parallel contraction, and spring-based flexible restoring mechanisms. A kinematic and dynamic mathematical model of the robot’s single-module structure was established. Simscape simulations were carried out to verify the kinematics and dynamics of the design. When compared with the calculated values from the mathematical model, the average error in the end-plate velocity of the kinematic module was merely 4%, and the average error in the dynamic load of the module was 4.58%. This validates the accuracy of the established mathematical model. Based on the configuration design, a prototype of the single module was fabricated. Load tests on the prototype revealed an average error of 8% compared to the calculated values of the dynamic model. Peristaltic crawling tests were conducted in pipes with three different diameters. The results demonstrate that the proposed rigid-flexible coupled pipeline robot has effective peristaltic crawling capabilities in both straight and curved pipelines. These findings also emphasize the robot’s high robustness to different pipe diameters.