Development of a Robot Combining a Hyper-Extension Unit and an Earthworm-Type Robot Enhancing Propulsion and Traction

<p>This paper proposes a robot that combines a hyper-extension unit at the front with an earthworm-type robot at the rear, designed to inspect long, narrow, and complex pipelines. In conventional in-pipe inspection robots with simple designs, there was no mechanism for the robot to effectively exert traction and propulsion while optimizing speed according to the required force. Therefore, this paper describes the development of a robot that combines a hyper-extension unit at the front, which achieves an elongation rate of approximately 300% even at low expansion rates, with an earthworm-type robot at the rear. The developed robot can operate in two patterns: pattern 1 combines the movements of an earthworm and an inchworm, while pattern 2 resembles that of an inchworm. It can switch between speed and force modes by changing its motion pattern. Experimental comparison of the horizontal straight pipe movement speeds of pattern 1 and pattern 2 without and with load showed that pattern 2 was 3.32 times faster than pattern 1 without load and that pattern 1 was 1.51 times faster than pattern 2 with load, clarifying the importance of changing robot’s motion pattern according to the load. The vertical pipe movement speed without load was 3.04 times faster in pattern 2 than in pattern 1. The proposed robot traveled 1.43 times faster than the conventional robot equipped with a conventional spring mechanism when passing through the elbow pipe using pattern 1. However, it could not pass through the elbow pipe using pattern 2, showing the importance of changing the robot’s motion pattern when passing through bent pipes. These results indicate that the proposed robot has the potential to achieve more efficient inspection in long-distance, small-diameter, complex pipes by changing its motion pattern according to the situation in the inspection pipe.</p>