Challenge to Investigation of Fuel Debris in RPV by an Advanced Super Dragon Articulated Robot Arm: Design and Prototyping of a Lightweight Super Long Reach Articulated Manipulator

A long-reach articulated manipulator that can deploy various sensors in a large but confined workspace is urgently needed in decommissioning tasks at Fukushima Daiichi Nuclear Power Stations. The most critical problem involves managing the large gravitational torques acting on the manipulator’s joints. In previous studies, several prototype models were developed; however, they were extremely heavy and bulky. This paper presents fundamental ideas for creating a lightweight super long-reach articulated manipulator. First, a mechanical structure could be utilized to support gravity. Second, a vertical force could be generated to compensate for gravity. Third, a tendon-driven mechanism could be utilized because it permits the installation of heavy actuators on the base. The tendons can transmit the actuator power to each joint. Thus, the weight of the arm is significantly reduced. We have discussed the advantages and drawbacks of each recommendation based on the hardware prototyping.