AN ULTRAPRECISION POSITIONING SYSTEM USING A TWIST-ROLLER FRICTION DRIVE

For ultraprecision positioning, the use of the twist-roller friction d rive is proposed. To improve the positioning accuracy of conventional twist-roller friction drives, the proposed design has two features: (1 ) the twist angle between the driving shaft and the driven rollers is very small, and (2) the driven rollers are supported by hydrostatic be arings. The twist-roller friction drive is mechanically a kind of lead screw, and the small twist angle makes the lead of the friction drive less than 0.1 mm. The use of hydrostatic bearing is effective for imp roving the rotational accuracy of the driven rollers and for eliminati ng the influence of the fluctuation in roller rotation on positioning accuracy. It has been shown by experiments that the resolution of posi tioning can be less than 10 nm, and the twist-roller friction drive is suitable for an ultraprecision positioning system.