Compensation of temperature induced position measuring error in the ultra-precision moving robot system

In this paper, for measuring the position error of the ultra precision stage more accurately, the refractive index compensation method is introduced. The wave length of the laser interferometer is compensated using the simultaneously measured the variation of room temperature in the method. In order to investigate the limit of compensation, the stationary test against two fixed reflectors mounted on the zerodur plate is performed firstly. From the experiment, it is confirmed that the measuring error of the laser interferometer can be improved from 0.34 mu m to 0.11 mu m by the application of the method. Secondly, for the verification of the compensating effect, it is applied to estimate the positioning accuracy of a ultra precision aerostatic stage. Two times of the refractive index compensation are performed to acquire the positioning error of the stage from the initially measured data, that is, to the initially measured positioning error and to the measured positioning error profile after the NC compensation. Although the positioning error of the aerostatic stage cannot be obtained clearly, it is known that by the compensation method, the measuring error in the laser interferometer can be improved to within 0.1 mu m in the practical measurement on ultra precision stage.