Anisotropic shadow-based operation assistant for a pipeline-inspection robot using a single illuminator and camera

This paper presents an anisotropic shadow-based operation assistant method for a multilink-articulated wheeled pipeline-inspection robot by using a single illuminator and camera. By displacing the position of the illuminator relative to that of the head camera, a crescent-shaped shadow appears in the images captured in a bent pipe. The size, position, and orientation of the shadow depend on the robot's orientation around the pipe axis, and the shadow disappears in a certain robot's orientation (anisotropic shadow). Generally, as for shadow based navigation systems, disappearances of the shadow should be avoided because the robot loses its way. However, our previously developed robot (AIRo-2) adapts to a bent pipe without any control when the robot's orientation and the pathway direction of the bent pipe are aligned. By aligning those two specific orientations, we propose operation assistant system to pass through winding pipes. In this paper, the shadow region is extracted using two types of image binarization. The proposed system was experimentally verified in pipelines including seven bent pipes by applying the pathway direction of the bent pipe (obtained from the shadow) to the rolling movement of the robot.