Singular point analysis during rail deployment into vacuum vessel for ITER blanket maintenance

ITERブランケット保守用軌道の真空容器内への展開時における特異点解析

角舘 聡; 柴沼 清

Kakudate, Satoshi; Shibanuma, Kiyoshi

ITERブランケット遠隔保守では真空容器内の高い線(0.5kGy/hr)のために遠隔保守ロボット(保守ロボット)による保守が要求される。そのため、真空容器内のブランケット保守に適用する保守ロボットとしてビークル・マニピュレータシステムが開発された。本システムの主要な技術課題は駆動源がない8リンク構成の多関節軌道をドーナツ型真空容器内へ展開する軌道展開技術である。この技術課題を解決するために駆動源を関節部に有しない多関節軌道(リンク)の機構学的な解析モデルを提案した。提案した解析モデルは軌道展開時の軌道姿勢に関する特性方程式であり、特性方程式の微分関係式であるヤコビアンJ'の行列式det=J'を解析的に求めた結果、軌道展開時に多関軌道の姿勢が特定できずに制御が困難となる特異姿勢(特異点)の存在を明らかにした。この特異姿勢を回避するための具体的な方策として、新たな軌道展開シナリオを提案し、本提案シナリオを実規模装置に適用することによって軌道関節部に駆動源を持たない多関節軌道の軌道展開に関する成立性を確認した。

Remote maintenance of the ITER blanket composed of about 400 modules in the vessel is required by a maintenance robot due to high radiation of 500Gy/h in the vessel. A concept of rail-mounted vehicle manipulator system has been developed to apply to the maintenance of the ITER blanket. The most critical issue of the vehicle manipulator system is the feasibility of the deployment of the articulated rail composed of eight rail links into the donut-shaped vessel without any driving mechanism in the rail. To solve this issue, a new driving mechanism and procedure for the rail deployment has been proposed, taking account of a repeated operation of the multi-rail links deployed in the same kinematical manner. The new driving mechanism, which is deferent from those of a usual articulated arm equipped with actuator in the every joint for movement, is composed of three mechanisms. To assess the feasibility of the kinematics of the articulated rail for rail deployment, a kinematical model composed of three rail links related to a cycle of the repeated operation for rail deployment was considered. The determinant det J of the Jacobian matrix J was solved so as to estimate the existence of a singular point of the transformation during rail deployment. As a result, it is found that there is a singular point due to det J =0. To avoid the singular point of the rail links, a new location of the second driving mechanism and the related rail deployment procedure are proposed. As a result of the rail deployment test based on the new proposal using a full-scale vehicle manipulator system, the respective rail links have been successfully deployed within 6 h less than the target of 8 h in the same manner of the repeated operation under a synchronized cooperation among the three driving mechanisms. It is therefore concluded that the feasibility of the rail deployment of the articulated rail composed of simple structures without any driving mechanism has been demonstrated.