Remote Handling Control System and Operations of Vacuum-Compatible In-Vessel Inspection System

The plasma-facing components (PFCs) in a tokamak require periodic in-service inspection to allow for the detection of any damage or wear due to the exposure to the high heat flux and plasma radiations so that repairs or replacement can be made before the damage becomes severe. The inspections must be done without breaking the ultrahigh vacuum (UHV) to maintain the machine availability. An in-vessel inspection system (IVIS) compatible to vacuum and high temperature has been developed for the in-service inspection of tokamaks. The IVIS is compatible to 8e−8 mbar vacuum and $100~^{\circ }$ C temperature. The system consists of a 5-DOF articulated arm with a reach of up to 4 m to deploy inside the vacuum vessel carrying a vision device as a payload. It is mounted on a linear guide with a storage vacuum chamber (SVC) connected to the radial port of tokamak through a vacuum gate valve. The IVIS arm consists of 05 revolute joints based on vacuum-compatible brushless dc motors with specially lubricated gearboxes and UHV-compatible multiturn absolute encoders. The IVIS system is controlled remotely using a closed-loop virtual reality (VR)-based monitoring and control system. The IVIS control system is built on CAN-Open network architecture and includes high-precision servo drives with position feedback from Hall sensors and absolute encoders. During initial testing, the position repeatability of ±2 mm has been achieved. The system can also be adapted for inspection and maintenance in any large system with challenging environment such as vacuum, temperature, and narrow spaces. This article presents in detail the IVIS control system design and test results.