An underground explorer robot based on peristaltic crawling of earthworms

Purpose – An earthworm moves by peristaltic crawling which brings a large surface into contact during motions and requires less space than other mechanisms. A peristaltic crawling is suitable for moving in excavated space by an anterior (front) of a robot. Therefore, a peristaltic crawling robot is useful for an underground explorer. The purpose of this paper is to develop a peristaltic crawling robot with several parallel links and compare with motion of an actual earthworm. Then we had some experiments on a plane surface and in a tube, and in vertical perforated dirt. Design/methodology/approach – The proposed robot, which consists of several parallel mechanisms, has four units for being controlled in 3‐DOF. A unit expands in a radial direction when it contracts to increase the friction between the unit and surroundings. Dustproof covering is attached for preventing dirt from getting inside units. Locomotion mechanism is as the same as an actual earthworm's peristaltic crawling. The robot makes an anterior unit contract, and then the contraction propagates towards the posterior (rear). Therefore, it requires no more space than that of an excavation part on the front of the robot. Findings – It was found that three units of robot consists of several parallel mechanisms had wide range of manipulation; four units of robot moves with peristaltic crawling compared with motion of an actual earthworm. It was confirmed that the robot could turn on a plane surface and move upward and downward in a vertical pipe. Finally, the robot could move in vertical perforated dirt faster than in a pipe. Originality/value – The robot is designed with several parallel links and equipped with dustproof covering. The locomotion of an actual earthworm is videotaped and analysed for comparing with the analysed movements of the robot. It was confirmed the robot could move with peristaltic crawling and turn on a plane surface. In addition, it was confirmed that some experiments were done in a narrow pipe and in vertical perforated dirt.