Research Of Macro-micro Positioning System Based On Diffraction Grating Metrology

Combined with the National Natural Science Foundation (project number: 50,605,018) "Study on Measurement Methods of Cross Diffraction Grating and Positioning Technology of XY Stages", a diffraction grating measurement systems and macro-micro positioning system with diffraction grating as displacement measurement sensor is designed and analyzed. The optimization method and the control algorithm have been verified by experiments. It improves the deficiency of the positioning speed and the positioning accuracy for long stroke, high-precision positioning systems at present. The specific studies are as follows:Firstly, Combined with the structural analysis of the macro-micro driving stage, a precise positioning system which composed of double diffractive gratings measurement equipment and driving system with AC servo motor and PZT has been designed.Secondly, the measurement system base on diffraction grating has been designed and completed. The measuring principle of diffraction grating and the method of obtaining grating interference strips and displacement numerical value are expatiated. The environmental noise has been weakened effectively by signal processing with AC modulation. Aiming at the deficiency of DC drift and non-automatic, a method of automatic compensation based on PWM has been realized. And the software subdivision and error compensation has been finished for improving the measurement precision.Thirdly, the working principle of the macro positioning system, and the control of servo motor has been completed. The accuracy of the self-positioning equipment of the driving system is analyzed by mathematical statistics method. According to the stability analysis of macro positioning system, an effective method of improving the stability analysis has been designed. Based on the high accuracy grating arithmetic equipment, a macro positioning algorithm has been designed, and with experimental verification, the algorithm has the characteristics of high stability, high speed and high accuracy.Fourthly, combined with the mechanical analysis and experimental tests, the natural frequency has been determined. The high voltage driving circuit has been designed and realized. The stabilization, static and dynamic characteristics has been analyzed. According to the hysteresis of PZT, a micro positioning algorithm based on maximal slope method has been designed, and procures all right effects.Finally, according to the characteristics, the combination of macro and micro positioning has been realized to complete the precision positioning experiment.In this paper, theory study and experimental verification is operated to establish the soft and hard environments. According to the research of the grating measurement accuracy, static and dynamic characteristics and stabilization, methods of error compensation and algorithms are designed and implemented. Experiments showed that the positioning system realizes the unification of high speed and high accuracy of long stroke positioning system, and provide support to the research of precision positioning system.