SUBMICROMETER OVERSHOOT CONTROL OF RAPID AND PRECISE POSITIONING

Precise-positioning technique is relatively well developed. However, i t is still difficult to avoid an overshoot or to limit the overshoot w ithin a submicrometer in a rapid and precise positioning. Inspired by recent studies on microdynamics, a control algorithm based on the vari able structure control (VSC) method is proposed to achieve an overshoo t smaller than 0.2 mu m and rapid, precise positioning (a 0.5 mm simil ar to 1 cm positioning with a steady-state error smaller than 30 nanom eter in 0.5 s) with a linear motor drive stage. The stage is guided by a rolling ball guide and with a 10 nm resolution laser interferometer as its position sensor. Some characteristic values in the friction mo del of microdynamics are included to design the controller. Therefore, we found a way to achieve rapid, precise, and small overshoot positio ning by combining mechanism design, system identification, lubrication , and controller design techniques. (C) Elsevier Science Inc., 1997.