Research On Urtra-precision Positioning System Based On Phase Tracking Feedback Mechanism

With the continuing development of precision machining, semiconductor device manufacturing, integrated manufacturing industry and biological engineering research, the precision positioning technology has been developing rapidly, and its precision level has transformed from micro to nanometer. The architecture of traditional positioning system is testing-control-execution. The positioning accuracy of the system is improved through the constant development of the technology of each unit module. At present, because of the limitation of working principle and machining technology, the precision of each unit module is increased slowly as the performance of each unit module is close to the limit of the current technological level.From the structure of positioning system, a new method of ultra-precision positioning is presented based on phase tracing feedback mechanism. The phase difference of beat frequency signal in the process of double frequency laser interference is transformed into the driving signal to simplify the output link of the transform between the phase difference and the measurement of displacement. The method reduced the error sources that affect the positioning accuracy of the system output, and thus the precision and the stability of the positioning system are improved.The theory method, error sources and the key technology of the phase tracking feedback mechanism of the ultra-precision positioning system are studied deeply and systematically in this dissertation. The main research work is as follows:The traditional monitoring unit of positioning system is replaced by the phase locking unit of reference signal and the measured signal in the heterodyne double-frequency laser interferometer. The phase difference replaces the displacement measuring data of the interferometer as the control signals of drive unit. It proves the feasibility of ultra-precision positioning based on phase tracking feedback mechanism. According to the requirements of the nanometer scale precision positioning, ultra-precision positioning system, including laser interferometer system, phase tracking control unit, drive unit and micro displacement platform unit, have been designed.According to the principle and technical requirements of phase tracking control, positioning system control unit, including high frequency signal generation and phase shift module, high frequency phase discrimination module and bipolar drive module, are designed and developed. The working principles have been analyzed and the circuit structure, function and realization process of each module were presented. The output signal and the main factors influencing the accuracy of circuit are discussed. A fixed phase difference of two high precision20MHz signals is produced by producing640MHz high frequency signal and phase shifting method to ensure the accuracy of the phase tracking and positing driver. Piezoelectric ceramic actuator with high precision, low ripple, double polarity is designed by using the method of RC compensation to eliminate the self-excited oscillation. The traditional driving method of presetting voltage is improved and the convenience of bidirectional position is promoted.With the demand of nanometer scale localization, the mechanical structure and driving method of the micro-displacement platform are discussed. Typical characteristic parameters and output rotation stiffness of flexure hinge are analyzed systematically and the output characteristics of right circular, elliptical, hyperbolic and parabolic flexure hinge are presented. The structure of micro-displacement platform in the positioning system is designed and the micro-displacement stiffness, maximum stress, natural frequency and other characteristics are analyzed. ANSYS is used to optimize the flexure hinge and parallel four-bar structure parameters. Parameter adjustment is used to achieve rapid design of micro-displacement platform.Various error sources that affect the positioning accuracy in the process of phase tracking feedback positioning system are analyzed in detail. Main research includes system error of the mechanical unit, circuit unit, instruments and equipment units, as well as random error like environmental error, temperature error, electromagnetic interference and so on. These errors are analyzed quantitatively and the change laws have been made clear. The accuracy of the positing system is improved by eliminating or reducing the error by compensation and suppression methods. In order to realize the actual engineering application that promotes the accuracy of the positioning system with low cost and high efficiency, a comprehensive compensation method of binary function is presented based on a priori data. The method can simplify the compensation calculation with the same accuracy compared to traditional binary function integrated method.Finally, the main part and the whole positioning system are tested. The experiments on high frequency phase discrimination and bipolar drive circuit have been performed. The tests for the resolution, stability, repetitiveness performance of the positioning system output is carried out. The errors including mechanical unit, circuit unit, equipment, environmental factors have been detected quantitatively and all of the error factors have been synthesized to confirm the uncertainty of the positing system. The results show that the uncertainty is11.7nm in the positing range of52μm.A new ultra-precision positioning method based on phase tracking lock as a kind of displacement monitoring unit with no traditional sense is explored. Further study on the characteristics of the ultra-precision positioning system, the design of micro displacement platform and compensation for system error is carried out based on the new method. It provides a new method for further development of nanometer scale positioning system. The methods in the field of the compensation for precision drive and multiple parameters are supplied and improved. It has a broad application prospect in the fields of ultra-precision integrated manufacturing and nanometer science and technology.