Vision Guided Robotic Stacking of Pellets to a Fixed Length

Nuclear fuel pellets are stacked to a fixed length before they are inserted into a tube to make a fuel pin. We describe here the development of a vision guided robotic system that rearranges the pellets in a tray such that each row in the tray attains desired stack length. The proposed system uses line scan cameras that can measure lengths of individual pellets to an accuracy of 100 micron. In order to perform required rearrangement of pellets, a search algorithm is devised that minimizes the number of pellet movements. Pellets are moved by a high precision and high speed articulated robot. The paper describes the overall approach and the algorithm for deciding pellet movements.