Research On Control Method And Software Design Of Beat-frequency Fabry-Perot Laser Interferometry System

Laser interferometry is widely used in the field of chip processing,high-precision equipment manufacturing and other precision detection because of its high accuracy,good resolution and large measurement range.The continuous improvement of manufacturing accuracy has put forward higher and higher requirements for the production technology level,which makes the relevant high-precision measurement technology accuracy must be improved accordingly.The frequency beat Fabry Perot(F-P)laser interferometry can trace the measurement of displacement,strain and other conventional geometric quantities to time and frequency.In theory,the measurement accuracy can reach the level of PI meter,and the measurement accuracy can meet the measurement system accuracy requirements of modern production process measurement technology.Therefore,it is of great significance to develop high-precision beat frequency F-P laser interferometry technology.This thesis introduces the research status of beat frequency F-P Interferometry Technology and common control methods at home and abroad,describes the principle of beat frequency F-P laser interferometry,analyzes the working characteristics of related instruments and equipment of the measurement system,and points out the necessity of optimizing the design of fretting control and transmission light intensity peak locking control in the whole measurement process.Firstly,a digital incremental trapezoid PID control method based on integral separation is proposed to optimize the control performance of the micro motion system,so as to improve its positioning accuracy;secondly,the fuzzy PID control method optimized by neural network is used to improve the control performance of the transmitted light peak locking,so as to improve the light peak locking accuracy of the measurement system.In order to effectively eliminate a variety of small amplitude high-frequency noise in the actual data acquisition process,a recursive anti pulse average filtering method combining the advantages of recursive filtering,median filtering and arithmetic average filtering is proposed,which improves the signal quality of the acquired beat frequency signal and transmitted light intensity signal.In view of the problems of low efficiency and poor real-time performance in the parallel execution of multiple functions of measurement and control software,a software design method based on lightweight parallel programming is proposed,which parallelizes the original measurement and control function modules for task processing,thus improving the actual operation performance of measurement and control software.Finally,the experimental device of the measurement system is built.The performance of the beat frequency F-P laser interferometry system is verified by the control performance test of the fretting system,the transmission light intensity peak locking control performance test and the nonlinear error measurement.The experimental results of the control performance of the fretting system show that after the digital incremental trapezoid PID control method based on integral separation is applied to the fretting system,the standard deviation of the positioning of the fretting system in the range of 0.8?m is increased from 7.63nm to 0.86 nm,and the standard deviation of positioning in the range of 15?m is increased from 10.02nm to 1.31nm,which proves the effectiveness of the micro motion control method.The experimental results show that after the fuzzy PID control method optimized by neural network is loaded into the measurement system,the transmitted light intensity can be locked to the vicinity of the transmitted light intensity peak of 110mV continuously,and its standard deviation is about 2.49mV.The peak intensity of the reference transmitted light intensity before optimization is higher and more accurate.The experiment of nonlinear error measurement shows that the maximum and minimum of nonlinear error measured by beat frequency F-P laser interferometry system are 1.79nm and-1.32nm respectively,which have obvious periodicity and are basically consistent with the nonlinear error given in the standard test report.These performance test results show that the optimized beat frequency F-P laser interferometry system has the uncertainty of non-linear error measurement in the micro nano measurement range,which verifies the feasibility and effectiveness of the relevant control algorithm and software optimization method used in this thesis.