機能化送りねじ機構 : 第2報,バックラッシの実時間計測と除去

抄録

An active lead screw mechanism (ALSM) has been proposed as an ultraprecision positioning mechanism at a high speed. The ALSM is able not only to control backlash between a screw and a nut but also to position a table by piezoelectric actuators. In order to realize this ability, the ALSM must have access to a set of backlash data or be capable of real-time measurement of the backlash. In the first report, the backlash was measured beforehand as a function of the rotation angle of the lead screw, which required a tremendous amount of labor. First this report describes the real-time measurement and the elimination of the backlash. The frictional force between the screw and the nut depends on the backlash. In this paper, the backlash is measured using the change of frictional force. Then the positioning controller is improved to reduce the positioning time. In order to reduce the overshoot, the coarse-positioning controller (P-D) changes the proportional gain according to the deviation. In order to quickly reduce the residual vibration caused by coarse-positioning, the parameters of the fine-positioning controller (PI-D) were changed.