Pneumatic Duplex-Chambered Inchworm Mechanism for Narrow Pipes Driven by Only Two Air Supply Lines

Small in-pipe robots are key to improving pipe inspection procedures, especially for narrow diameters. However, robotic locomotion in such spaces, namely achieving a high locomotion performance with a narrow and flexible mechanism, is difficult. The novel in-pipe locomotion mechanism proposed in this letter achieves rapid locomotion through narrow pipes by a unique duplex-chambered structure. The mechanism achieves smooth bi-directional inchworm locomotion by a combination of expandable silicone rubber and a coil spring and is fully controlled by only two air supply lines. The concept and locomotion technique, including a mathematical analysis and discussion from the viewpoint of operational pressure, are presented herein. Several experiments on the prototyped mechanism were performed to elucidate its characteristics. The results of locomotion tests through horizontal, vertical, and bent pipes showed that the mechanism can horizontally navigate through 25-mm pipes at 45.5 mm/s, which is the fastest yet reported for this size of bi-directional in-pipe robot.