Visual inspection and motion control for invessel tile servoing tasks in a Tokamak vessel

This paper presents a generalised framework of an image based visual servoing of an articulated arm which has to be deployed inside a simulated Tokamak vessel environment. First wall tiles of the vessel idealised as rectangular grids on a surface are inspected and an attempt is made to replace the damaged tiles with a tile-screwing gripper mechanism. The mechanism of gripper provides compactness and high torque capacity in gripping with pitch and roll as degrees of freedom. The gripper is considered as a class of unknown nonlinear discrete-time system. The gripper mechanism is implemented for unscrewing a square headed screw on the first wall tiles of the vessel. Various stages of tile handling task are explained in detail with theoretical modeling. The vision sensing methodology of the proposed arm is explained. The arm has a camera located at the wrist (end effector) and the control action has to be taken in place at joint level. The kinematics of the manipulator, vision system employed are explained. The preliminary results are illustrated. The camera attached to the end effector and the captured image processing for prediction of type of fault and the gripper tactile sensing issues as well the faulty tile removal are explained.