Analysis of Measuring Precision of 3D Model of Ishigaki Stone in Kumamoto Castle Using Automatic CMG Crane System

Abstract

Kumamoto Castle, consisting of towers and stone walls called Ishigaki, was severely damaged by the 2016 Kumamoto earthquake. As this castle has cultural significance in Japan, the damaged stone walls of the castle need to be promptly and accurately restored. In recent years, the utilization of 3D stone data has been studied to determine the position of collapsed stones precisely. The 3D stone data needs to be measured automatically in a short period of time for the efficient restoration of stone walls. To control the attitude of the stone, a small control moment gyro (CMG) device was proposed, and a robust controller with a model error compensator was applied to the CMG device. In this study, the measurement precision of a 3D model of stones using the CMG crane system was analyzed. The automatic measuring system consists of a CMG device and an elevator for a 3D scanner to reduce the load on workers. The scanning motion was planned automatically based on the shape and position of stones using depth sensors. The effectiveness of the proposed measuring system was evaluated using the accuracy and measurement time including the data correction time of the 3D modeling.