This study proposes a robot that can crawl through the bottom of tanks and measure the thickness of its floor plate using an ultrasonic sensor. To prevent the robot from toppling because of the fluid resistance of the oil and to direct the transducer of the ultrasonic sensor perpendicular to the floor plate, a design inspired by a roly-poly toy was implemented. This ensured that the robot remained upright owing to the separation of its center of gravity and center of buoyancy. However, although this structure makes the robot resistant to toppling, it makes it susceptible to tilting owing to fluid resistance. Therefore, a simulator was developed, as part of this project, to estimate the robot’s posture in liquid. Finally, experiments were conducted in an indoor water pool under the assumption of the oil tank to compare the postures estimated by the simulator and actual posture.
Yokoyama et al. (Thu,) studied this question.