Study of a robotic system to detect water leakage and fuel debris -System proposal and feasibility study of visual odometry providing intuitive bird's eye view

Abstract

To obtain the necessary information of the fuel debris and water leakages in the decommissioning task of Fukushima Daiichi nuclear power plants, an ultrasonic-based investigating method had been proposed towards the future internal investigation of the Primary Containment Vessel (PCV). In this article, we studied the assisting mechanisms and methods for the investigating method, as the rotatable winch mechanism and visual localization method. We used the rotatable winch mechanism to adjust the height and orientation of the ultrasonic sensor and localized the robot with cameras to localize the sensor, as assisting information for data combination. We studied the feasibility of the conventional visual odometry method of applying to the situation and performed localizing accuracy evaluating experiments with a mobile robotic platform prototype. Results showed that the visual odometry method could generate intuitive maps from bird’s eye view, and provided the average error rate of 35mm/1500mm, which met the required error rate for grating movement. The adjustable parameter ranges that could provide the required accuracy were also conducted.