SPIRA: Small Gas Pipeline Inspection Robot with Spiral Leg-Wheel Mechanism and Single Bending Joint

Abstract

Gas pipelines damaged by aging or earthquakes need a robotic system that can quickly inspect 50-mm-diameter service lines, consisting of horizontal and vertical pipes connected by elbow joints, tees, or sockets, from the inside. However, conventional pipe inspection robots do not target 50-mm pipes and various pipe types or lack sufficient speed and a reverse function. Thus, this study develops an inpipe inspection robot, SPIRA, capable of traveling through 50-mm pipelines while meeting the above requirements. SPIRA has three wheels inclined at 30 degrees to the horizontal, arranged around a cylinder. The cylinder is rotated by a motor around the robot’s axis, and the wheels move in a spiral motion while pushing the pipe wall, enabling the robot to move stably and quickly. To overcome socket steps of up to 3 mm and diameter changes in elbow joints, the cylinder and each wheel are connected by a leg with a spring pantograph mechanism. SPIRA has two traveling units linked by a bending joint with a servomotor. When the front and rear parts rotate clockwise (counterclockwise), SPIRA moves forward (backward). When both units rotate in the opposite direction, only the central part of SPIRA rotates on the spot, changing the bending direction so that SPIRA can select any travel direction in a tee. We evaluated the travel performance of SPIRA in a pipeline of horizontal, vertical, elbow joints, tees, or sockets, and found that it could smoothly travel through the pipelines, which is difficult for conventional robot systems to achieve.