Abstract
A tri-mode two-axis picometer positioning system is proposed. The proposed system has coarse, fine and ultra-fine mode. The coarse and fine positioning modes are driven by the twist-roller friction drive and controlled by a numerical control system. The ultra-fine mode is driven by the active aerostatic guideway using the active inherent restrictors and controlled by a personal computer. Measured positioning resolution in the coarse mode is 5nm and that in the fine mode is 1nm. In the ultra-fine mode, current positioning resolution is 50pm, however, the picometer order of positioning resolution is expected.