Papers by Author: H. Tachikawa

Abstract: This paper deals with nanometer positioning in the presence of friction. The object studied is a ball-screw-driven and linear-ball-guide-supported table system. For this system, the friction dominates the resulting performance for micro-motion and the system exhibits microdynamic characteristic which is rather different from macrodynamics. Inherently a controller with high loop-gain is needed to suppress the effect of friction. A PID controller is designed for the table system for step height smaller than 10μm. Experiment and simulation results indicate that the PID controller can provide a sufficiently high-loop gain and effect of friction is suppressed. In point-to-point(PTP) positioning for step heights from 10μm down to 10nm, the positioning error is within ±2 nm and the response dynamics is satisfactory.

Abstract: This paper deals with nanometer positioning in the presence of friction. The object researched is a ball-screw-driven and linear-ball-guide-supported table system. For such system, models that do not account for friction can only be applicable to describe the macrodynamic behavior which is significantly different from the microdynamic one. A PID controller is designed with high-loop gain to suppress the effect of friction. The controller parameters are calculated by pole placement according to macrodynamics, no identification of friction and friction model are necessary. Experiment and simulation results indicate that nanometer positioning can be realized in this system by the controller. In point-to-point (PTP) positioning for step heights from 0.1μm to 1mm, the positioning error is within ±5 nm and the response characteristics are satisfactory.