ULTRAPRECISION POSITIONING USING LEAD SCREW DRIVE (2ND REPORT) - NANOMETER LEVEL POSITIONING BY MODIFYING PROPORTIONAL GAIN CHARACTERISTIC

In the first report, the quantified offset error was caused by the dea d band of the proportional gain which exists in the D/A converter and the personal computer, when a position feedback control was applied to a one-dimensional table unit driven by the lead screw. Therefore, in this report the gain characteristic is modified by eliminating the dea d band with a new control method called ''Bit control''. As a result, both the deviation positioning error (mean error) and the dispersion p ositioning error (standard deviation) can be decreased to nanometer le vel. In addition, the characteristic differences between the ball scre w and sliding screw are clarified at the very small table displacement ; The ball screw has an elastic characteristic between the screw and nut. The sliding screw has a stick-slip between them.