Traction Amplified Actuation System for Inspecting Narrow and Complex Pipes Using Enhanced Linear Antagonistic Mechanism-Bend Pipe Passage Model and Force Comparison

This paper describes the design, experiments, and quantitative force comparison of a Pipe Inspection RObot named PI-RO II using the enhanced linear antagonistic mechanism to amplify the traction. This study aims to develop an inspection robot for long, narrow, and complex pipes requiring large traction, propulsion, and flexibility. Many types of pipe inspection robots using soft pneumatic actuators were proposed in conventional studies, focusing on compatibility, high-power characteristics, and flexibility. In a previous study, we proposed a linear antagonistic mechanism allowing the inspection robot to generate both high traction and propulsion with flexibility in narrow pipes. The large extension force of an extension actuator is distributed to the traction and propulsion. However, when large propulsion was required, traction was insufficient because the extension force of an actuator was distributed to traction and propulsion. Furthermore, the traction is decreased because the actuator's elongation/contraction length is absorbed due to the changing robot's movement path in the bending pipe. This paper described an enhanced linear antagonistic mechanism that amplified traction through the active force of multiple integrated pneumatic actuators even when large propulsion is required. Moreover, a design method is explained to keep PI-RO II 's axis consistent with the center of the pipe. PI-RO II in this study inspected an upward pipeline with a length of 4.5 m, including 5 elbow pipes three times consecutively within approximately 1250 s, respectively. The function value that compares the traction and propulsion considering the effects of the applied pressure and pipe diameter required for long-distance inspection is more than 1.79 times that of the other related studies. This function value allows a comparison of the sum of traction and propulsion values of various pneumatically driven pipe inspection robots by non-dimensionalizing the inner diameter of the pipe and the pressure. This result shows PI-RO II has the possibility to generate large traction even when large propulsion is required. Therefore, we believe that the proposed mechanism will improve the moving efficiency of the pipe inspection robots.