An In-Pipe Mobile Robot for Use as an Industrial Endoscope Based on an Earthworm’s Peristaltic Crawling

Many pipe accidents caused by corrosion or deterioration have been reported recently; hence, in-pipe inspection is needed to prevent such problems. Fiberscopes are currently used as industrial endoscopes to inspect defects in pipes. Because of friction, however, they cannot be inserted into pipes that are more than 15 m long or into complex pipes such as elbows. Therefore in-pipe inspection robots need to be selfpropelled in order to be inserted into these environments. We are developing a robot capable of propelling itself through various pipes, such as long pipes and elbow pipes, specifically, a peristaltic crawling robot using DC brushless motors for in-pipe inspection. In this study, the robot we developed was used in straight and elbow pipes with an inner diameter of 27 mm. In this paper, we derive theoretical formulas for robot locomotion speed and propulsion force and propose a special motion pattern, known as the middle motion pattern, for the robot’s peristaltic crawling pattern. We performed several experiments in a 27-mm-diameter acrylic pipe to examine the locomotion speed and propulsion force. We also developed a robot that can pass through an elbow and conducted several experiments to confirm this.