Abstract: For large-diameter precision rotating platforms,to adopt traditional methods to implement high-precision angular measurement is difficult.In order to solve this problem,a rotating angle measurement and compensation method for a single degree-of-freedom rotating platform is proposed on the basis of the spatial coordinates obtained by using a laser tracker.First,on the basis of the geometry theorem that a unique circle can be determined by any three non-collinear points,a mapping function between the rotating angle and the spatial coordinates is formulated.Through a comprehensive analysis of the relationship between the measurement error of the laser tracker and the angular error of the rotating platform,a criterion for the selection of measured radius and angle interval is made so as to fully utilize the measurement accuracy of the laser tracker to realize a high-precision measurement of the rotating angle error.Then,the polynomial interpolation method is utilized to obtain the change laws of the rotating angle error with the rotating angle position,and the real-time compensation of the rotating angle error is realized by embedding the fitted error mapping function into the control system and by modifying the output display of grating.Finally,the proposed method is applied in a calibration experiment on a precision rotating platform equipped with circular gratings.The results show that the proposed method can effectively reduce the angular error caused by the assembly error of circular gratings,which decreases from 40″ to 5″.

Key words: precision rotating platform, grating measurement, calibration, laser tracker