AN ANGSTROM-POSITIONING SYSTEM USING A TWIST-ROLLER FRICTION DRIVE

We propose a positioning system with an angstrom resolution. The posit ioning system has a table guided by a hydrostatic guideway, and a twis t-roller friction drive is incorporated into the table. The friction d rive converts the rotation of an AC servo driving motor into the linea r motion of the table. The twist-roller friction drive is advantageous for ultraprecision positioning, because ifs lead can be less than 0.1 mm. Monitoring the displacement of the table by a fiber optic displac ement sensor, a microcomputer in the system controls the rotational an gle of the AC servomotor Step positioning with several step widths is executed, and it is proved that the positioning resolution is 0.2 nm ( 2 Angstrom). The stroke of the system can be several hundred millimete rs. Thus, it is shown that the twist-roller friction drive is suitable for the angstrom-positioning system.