A V-shaped In-pipe Robot Capable of Drawing Route Maps for Both 3-in and 4-in Diameters using Only Low-cost Internal Sensors

Abstract

This paper proposes an in-pipe robot capable of creating route maps for narrow pipelines with inner diameters of both 3-in and 4-in. Pipe route-drawing often relies on external sensors, such as cameras and light detection and ranging (LiDAR). However, due to lighting, dirt, and spatial constraints within the pipeline, miniaturization has been challenging. Therefore, our method uses only internal sensors, such as a tiny inertia measurement unit (IMU), for robot posture acquisition and an encoder for distance measurement. Furthermore, a sensor-less joint torque control system was also implemented by using a specially designed printed circuit board with motor current regulation, allowing the robot to traverse the pipeline while suppressing excessive torque generation and slippage. The experiments to verify the performance of our route-drawing method were conducted on two types of pipelines with 3-in and 4-in inner diameters. It was revealed that the mean absolute error in the length of the straight sections was within 3% for all pipes, that in the rotational angle of the bent pipes was within 2 deg, and that in the direction of the straight pipes was within 2 deg.