A Pipeline Route Drawing System Equipped With a Towed Unit Using Only Low Cost Internal Sensors

Conventional systems for drawing pipeline routes from inside of the pipe often use external sensors such as cameras or lasers, but these can be easily affected by the illumination inside of the pipes and the material. Additionally, many of these sensors are high cost and too large to be implemented in small-diameter pipes. Therefore, this study proposes a pipeline route drawing system that uses a towed unit with only low cost internal sensors, which is towed by a self-propelled in-pipe inspection robot. This unit is equipped with only an internal measurement unit (IMU) and an encoder, making it suitable for use in 3- and 4-in pipes without illuminating the inside. The present article describes the method of estimating transition points between straight and curved pipes, the direction of straight pipes after passing through curved pipes, and the position of the curved pipes to be interpolated. Following this, the developed towed unit is used to perform route drawing experiments. The mean absolute error of the route dimension was 1.38% or less under all conditions, and the mean error in estimating the straight pipe direction was approximately 1.35° or less.